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who gave 


Lectures on Heat and Chemieal Elements, 
Delivered in those Cities in 1807 ; 




wbo have 






T was the author's intention when this work was put 
to press to publish it entire in one volume ; but he is 
now induced to publish it in two parts, for reasons 
which it may be proper to announce. 

Various essays of his were read before the Literary 
and Philosophical Society of Manchester, chiefly on 
heat and elastic fluids, and were published in the 5tb 
Volume of their Memoirs, in 1802, The new view* 
which these essays developed, were considered both 
curious and important. The essays were republished 
in several Philosophical Journals, and soon after 
tianslated into French and German, and circulated 
abroad through the medium of the foreign Journals. 
The author was not remiss in prosecuting his researches, 
in which he was considerably assisted by the applica- 
tion of principles derived from the above essays. In 
1803, he was gradually led to those primary Law«, 
which seem to obtain in regard to heat^ and to chemi- 
cal combinations, and which it is the object of the 
present work to exhibit and elucidate. A brief outline 
of them was first publicly given the ensuing winter in 
a course of Lectures on Natural Philosophy, at the 
Royal Institution in London, and was left for publica- 
tion in the Journals of the Institution ; but he is not 
informed whether that was done. The author has 
ever since been occasionally urged by several of his 
philosophical friends to lose no time in communicating 
the results of his enquiries to the public, alledging, that 
the interests of science, and his own reputation, might 


suffer by delay. In the spring of 1 807, he was induced 
to offer the exposition of the principles herein contained 
in a course of Lectures, which were twice read in 
Edinburgh, and once in Glasgow. On these occasiot^ 
he was honoured with the attention of gentlemen, 
universally acknowledged to be of the first respectability 
for their scientific attainments: most of whom were 
pleased to express their desire to see the publication of 
the doctrine in the present form, as soon as convenient. 
Upon the author's return to Manchester he began to 
prepare for the press. Several experiments required to be 
repeated ; other new ones were to be made ; almost 
the whole system both in matter and manner was to be 
new, and consequently required more time for the 
composition and arrangement. These considerations^ 
together with the daily avocations of profession, have 
delayed the work nearly a year ; and, judging from the 
past, it may require another year before it can be com- 
pleted. In the mean time, as the doctrine of heat, and 
the general principles of Chemical Synthesis, are in a 
good degree independent of the future details, there 
can no great detriment arise to the author, or incon- 
venience to his readers, in submitting what is already 
prepared, to the inspection of the public. 

MAY, 1808. 



Chap. i. On Heat or Caloric ----- i 
Section l . On Temperature ^ and the instru- 
ments/or measuring it - - 3 
. 2. On Expansion hy heat - - - 23 

. 3. On the specific heat of bodies - 47 

■ 4. On the Theory of the specific heat 

of elastic fluids ----- es 

.. 5. On the Quantity of heat evolved by 

combustion, &(c. - - _ - 75 
6. On the natural Zero of tempera- 
ture, or absolute privation of 
heat -------- 82 

— — 7. On the motion and communica- 
tion of heat, arising from in- 
equality of temperature - - 99 

■ — 8. On the Temperature of the atmo- 

sphere -------123 

■ 9. On the Phenomena of the Con- 

gelation of water - - - - 133 
Chap. ii. On the Constitution of Bodies - - 141 
Section 1. On the constitution of pure elastic 

fiuids - 145 

■ 2. On the constitution of mixed 

elastic fluids ------ 150 

— — — 3. On the constitution of liquids, and 
the mechanical relations be- 
twixt liquids atid elastic fluids J 94 
' ■ 4. On the constitution of solids - 208 
Ch.4P. III. On Chemical Synthesis - - - - 211 

JExplanaiion of the Plates - - 217 




» « W0IW 



HE most probable opinion concerning the 
nature of caloric, is, that of its being an elas- 
tic fluid of great subtilty, the particles of 
which repel one another, but are attracted by 
all other bodies. 

When all surrounding bodies are of one 
temperature, then the heat attached to them 
is in a quiescent state ; the absolute quantities 
of heat in any two bodies in this case are not 
equal, whether we take the bodies of ec-ual 
weights or of equal bulks. Each kind of 
matter has its peculiar aflBnity for heat, by 
which it requires a certain portion of the fluid, 
in order to be in equilibrium with other bodies 
at a certain temperature. Were the whole 


gjiantities of heat in bodies of equal weight or 
bulk, or even the relative quantitieSy accu- 
rately ascertained, for any temperature, the 
numbers expressing those quantities would 
constitute a table of specific heats, analogous 
to a table of specific gravities, and would be 
an important acquisition to science. Attempts 
of this kind have been made with very con- 
siderable success. 

Whether the specific heats, could they be 
thus obtained for one temperature, would ex- 
press the relation at evefy other temperature, 
whilst the bodies retained their form, is an 
enquiry of some moment. From the experi- 
ments hitherto made there seems little doubt of 
its being nearly so ; but it is perhaps more cor- 
rect to deduce the specific heat of bodies from 
equal bfdks than from equal iveights. It is very 
certain that the two methods will not give pre- 
cisely the same results, because the expansions 
of different bodies by equal increments of 
temperature are not the same. But before this 
subject can well be considered, we should first 
settle what is intended to be meant by the word 




And the Instruments for measuring it. 

The notion of the specific heat of bodies 
and of temperature, may be well conceived 
from a system of cylindrical vessels of different 
diameters connected with each other by pipes 
at the bottom, and a small cylindrical tube 
attached to the system, all capable of holding 
water or any other liquid, and placed per- 
pendicular to the horizon. (See Plate 1. Fig. 1.) 
The cylinders are to represent the different 
specific heats of bodies ; and the small tube, 
being divided into equal parts, is to represent 
the thermometer or measure of temperature. 
If water be poured into one vessel it rises to 
the same level in them all, and in the thermo- 
meter ; if equal portions be successively poured 
in, there will be equal rises in the vessels and 
in the tube ; the water is obviously intended 
to represent heat or caloric. According to this 
notion, then, it is evident that equal incre- 
ments of heat in any body correspond to equal 
increments of temperature. 

This view of the subject necessarily requires, 
that if two bodies be taken of any one tempe- 


rature, and then be raised to any other tem- 
perature, the additional quantities of heat 
received by each will be exactly proportioned 
to the whole quantities of that fluid previously 
contained in them. This conclusion, though 
it may be nearly consistent with facts in gene- 
ral, is certainly not strictly true. For, in 
elastic fluids, it is well known, an increase of 
hulk occasions an increase of specific heat, 
though the weight and temperature continue 
the same. It is probable then that solids and 
liquids too, as they increase in bulk by heat, 
increase in their capacity or capability of re- 
ceiving more. This circumstance, however, 
might not affect the conclusion above, pro- 
vided all bodies increased in one and the same 
proportion by heat ; but as this is not the case, 
the objection to the conclusion appears of va- 
lidity. Suppose it were allowed that a ther- 
mometer ought to indicate the accession of 
equal increments of the fluid denominated 
caloric, to the body of which it was to shew 
the temperature ; — suppose too that a measure 
of air or elastic fluid was to be the bodyj query, 
"whether ought the air to be suflTered to expand 
by the temperature, or to be confined to the same 
space of one measure ? It appears to me the 
most likely in theory to procure a standard 
capacity for heat by subjecting a body to heat. 


whilst Us bulk is kept constanthj the same. Let 
m z= the quantity of heat necessary to raise the 
elastic fluid 10* in temperature in this case ; 
then 771 -f- rf == the quantity necessary to raise 
the same 10°, when suffered to expand, fi being 
the difference of the absolute quantities of heat 
contained by the body in the two cases. Now, 
tV m = the quantity of heat necessary to raise 
the temperature 1° in the first case ; but 
T-V [m-i-d) can not be the quantity necessary in 
the second case ; it will be a less quantity in 
the lower degrees, and a greater in the higher. 
If these principles be admitted, they may be 
applied to liquids and solids ; a liquid, as wa- 
ter, cannot be raised in temperature equally by 
equal increments of heat, unless it is confined 
within the same space by an extraordinary and 
perhaps incalculable force ; if we suffer it to 
take its ordinary course of expansion, then, 
not equal, but increasing increments of heat 
will raise its temperature uniformly. If suffi- 
cient force were applied to condense a liquid 
or solid, there can be no doubt but heat would 
be given out, as with elastic fluids. 

It may perhaps be urged by some that the 
difference of heat in condensed and rarefied 
air, and by analogy probably in the supposed 
cases of liquids and solids, is too small to have 
sensible influence on the capacities or affinities 


©f bodies for heat ; that the effects are such, 
as only to raise or depress the temperature a 
few degrees ; when perhaps the whole mass 
of heat is equivalent to two or three thousand 
such degrees ; and that a volume of air sup- 
posed to contain 2005° of temperature being 
rarefied till it become 2000°, or lost 5° of tem- 
perature, may still be considered as having its 
capacity invariable. This may be granted if 
the data are admissible ; but the true changes 
of temperature consequent to the condensation 
and rarefaction of air have never been deter- 
mined. I have shewn, (Manchester Mem. 
Vol. 5, Pt. 2.) that in the process of admit- 
ting air into a vacuum, and of liberating 
condensed air, the inclosed thermometer is 
affected as if in a medium of 50° higher or 
lower temperature ; but the effects of instan- 
taneously doubling the density of air, or re- 
plenishing a vacuum, cannot easily be derived 
from those or any other facts I am acquainted 
with ; they may perhaps raise the temperature 
one hundred degrees or more. The great heat 
produced in charging an air-gun is a proof of a 
great change of capacity in the inclosed air. — 
Upon the whole then it may be concluded, 
that the change of bulk in the same body by 
change of temperature, is productive of con- 
siderable effect on its capacity for heat, but 


that we are not yet in possession of data to 
determine its effect on elastic fluids, and still 
Jess on liquids and solids.. M. De Luc found, 
that in mixing equal weights of water at the 
freezing and boiling temperatures, 32° and 212", 
the mixture indicated nearly 119" of Fahren- 
heit's mercurial thermometer; but the numerical 
mean is 122° j if he had mixed equal bulks of 
water at 32° and 2 12°, he would have found a 
mean of 115°. Now the means determined by 
experiment in both these ways are probably 
too high 5 for, water of these two temperatures 
being mixed, loses about l-90th of its bulk ; 
this condensation of volume (whether arising 
from an increased affinity of aggregation, or 
the effect of external mechanical compression, 
is all one) must expel a quantity of heat, and 
raise the temperature above the true mean. 
It is not improbable that the true mean tem- 
perature between 32° and 212° may be as low 
as 1 10° of Fahrenheit. 

It has been generally admitted that if two 
portions of any liquid, of equal weight but 
of different temperatures, be mixed together, 
the mixture must indicate the true mean tem- 
perature ; and that instrument which corres- 
ponds with it is an accurate measure of tem- 
perature. But if the preceding observations 
be correct, it may be questioned whether any 


two liquids will agree in giving the same mean 
temperature upon being mixed as above. 

In the present imperfect mode of estimating 
temperature, the equable expansion of mer- 
cury is adopted as a scale for its measure. 
This cannot be correct for two reasons; 1st. 
the mixture of water of different temperatures 
is always below the mean by the mercurial 
thermometer ; for instance, water of 32° and 
212° being mixed, gives 119" by the thermo- 
meter ; whereas it appears from the preceding 
remarks, that the temperature of such mixture 
ought to be found above the mean 122°; 2d. 
mercury appears by the most recent experi- 
ments to expand by the same law as water j 
namely, as the square of the temperature from 
the point of greatest density. — The apparently 
equal expansion of mercury arises from our 
taking a small portion of the scale of expan- 
sion, and that at some distance from the free- 
zing point of the liquid. 

From what has been remarked it appears 
that we have not yet any mode easily practi- 
cable for ascertaining what is the true mean 
between any two temperatures, as those of 
freezing and boiling water ; nor any thermo- 
meter which can be considered as approxima- 
ting nearly to accuracy. 

Heat is a very important agent in nature ; it 


cannot be doubted that so active a principle 
must be subject to general laws. If the phe* 
nomena indicate otherwise, it is because we 
do not take a sufficiently comprehensive view 
of them. Philosophers have sought, but in 
vain, for a body that should expand uniformly, 
or in arithmetical progression, by equal incre- 
ments of heat; liquids have been tried, and 
found to expand unequally, all of them ex- 
panding more in the higher temperatures than 
in the lower, but no two exactly alike. Mer- 
cury has appeared to have the least variation* 
or approach nearest to uniform expansion, and 
on that and other accounts has been generally 
preferred in the construction of thermometers. 
Water has been rejected, as the most unequally 
expanding liquid yet known. Since the publi- 
cation of my experiments on the expansion of 
elastic fluids by heat, and those of Gay Lussac, 
immediately succeeding them, both demon- 
strating the perfect sameness in all permanently 
elastic fluids in this respect ; it has been ima- 
gined by some that gases expand equally ; but 
this is not corroborated by experience from 
other sources. 

Some time ago it occurred to me as probable, 
that water and mercury, notwithstanding their 
apparent diversity, actually expand by the 
same law, and that the quantity of expansion 


is as the square of the temperature from their 
respective freezing points. Water very nearly 
accords with this law according to the present 
scale of temperature, and the little deviation 
observable is exactly of the sort that ought 
to exist, from the known error of the equal 
division of the mercurial scale. By prosecut- 
ing this enquiry I found that the mercurial 
and water scales divided according to the prin-^ 
ciple just mentioned, would perfectly accord, 
as far as they were comparable ; and that the 
law will probably extend to all other pure 
liquids j but not to heterogeneous compounds, 
as liquid solutions of salts. 

If the law of the expansion of liquids be such 
as just mentioned, it is natural to expect that 
other phenomena of heat will be characteristic 
of the same law. It may be seen in my Essay 
on the Force of Steam (Man. Mem. Vol. 5, 
Part 2.) that the elastic force or tension of 
steam in contact with water, .increases nearly 
in a geometrical progression to equal incre- 
ments of temperature, as measured by the coni' 
mon mercurial scale ; it was not a little sur- 
prising to me at the time to find such an ap- 
proach to a regular progression, and I was then 
inclined to think, that the want of perfect 
coincidence was owing to inaccuracy in the 
division of the received thermometer j but 


overawed by the authority of Crawford, who 
seemed to have proved past doubt that the error 
of the thermometer no where amounted to 
mare than one or two degrees, I durst not 
venture to throw out more than a suspicion at 
the conclusion of the essay, on the expansion 
of elastic fluids by heat, that the error was 
probably 3 or 4**, as De Luc had determined ; 
to admit of an error in the supposed mean, 
amounting to 12% seemed unwarrantable. How- 
ever it now appears that the force of steam in 
contact with water, increases accurately in 
geometrical progression to equal increments of 
temperature, provided those increments are 
measured by a thermometer of water or mer, 
cury, the scales of which are divided accord- 
ing to the above-mentioned law. 

The Force of Steam having been found to 
vary by the above law, it was natural to ex- 
pect that of air to do the same ; for, air 
(meaning any permanently elastic fluid) and 
steam are essentially the same, differing only 
in certain modifications. Accordingly it wz% 
found upon trial that air expands in geometri- 
cal progression to equal increments of tempe- 
rature, measured as above. Steam detache«l 
from water, by which it is rendered incapable 
of increase or diminution in quantity, was found 
by Gay Lussac, to have the same quantity ot 


expansion as the permanently elastic fluids. 
I had formerly conjectured that air expands 
as the cube of the temperature from absolute 
privation, as hinted in the essay above-men- 
tioned; but I am now obliged to abandon 
that conjecture. 

The union of so many analogies in favour 
the preceding hypothesis of temperature is 
almost sufficient to establish it; but one remark- 
able trait of temperature derived from expe- 
riments on the heating and cooling of bodies, 
which does not accord with the received scale, 
and which, nevertheless, claims special con- 
sideration, is, that a body in cooling loses heat 
in pi^oportion to its excess of temperature above 
that of the cooling medium ; or that the tem- 
perature descends in geometrical progression 
in equal moments of time. Thus if a body 
were 1000" above the medium ; the times in cool- 
ing from 1000° to 100, from 100 to 10,and from 
10 to r, ought all to be the same. This, 
though nearly, is not accurately true, if we 
adopt the common scale, as is well known > 
the times in the lower intervals of temperature 
are found longer than in the upper ; but the new 
scale proposed, by shortening the lower de- 
grees, and lengthening the higher, is found 
perfectly according to this remarkable law of 


Temperature then will be found to have four 
most remarkable analogies to support it. 

1st. All pure homogenous liquids, as water 
and mercury, expand from the point of their 
congelation, or greatest density, a quantity 
always as the square of the temperature from 
that point. 

2. The force of steam from pure liquids, 
as water, ether, &c. constitutes a geometrical 
progression to increments of temperature in 
arithmetical progression. 

3. The expansion of permanent elastic 
fluids is in geometrical progression to equal 
increments of temperature. 

4. The refrigeration of bodies is in geo- 
metrical progression in equal increments of 

A mercurial thermometer graduated accord- 
ing to this principle will differ from the ordi- 
nary one with equidifferential scale, by having 
its lower degrees smaller and the upper ones 
larger ; the mean between freezing and 
boiling water, or 122° on the new scale, will 
be found about 1 10° on the old one. — The 
following Table exhibits the numerical calcu- 
lations illustrative of the principles inculcated 





vals of 


- 68° 


- 2» 

- 18 

- 8 










or intet- 
vals of 

4 7908 




9 3063 

n. 769^3 
la 5903 
13 0008 




Same as 
— 40« 
or Faren 




24 0843 
3a 2943 








Force of 

Force of , 


sion of 

on of air 

vapour of 

vapour of 

scale; or 















rected for 










of glass. 

692 — 

In. M. 

Inch M. 












899 — 










965. « 



















47 — 









11. aa 




13 77 










' 20,65 










31. ~ 

no. — 








• 46.54 











152 — 





163 a 


I281 8 



'75 — 








17 19 




I351 8 


»93 — 

212. — 











Explanation of the Table. 

The first column contains the degrees of 
temperature, of which there are supposed to 
be 180 between freezing and boiling water, 
according to Fahrenheit. The concurrence 
of so many analogies as have been mentioned, 
as well as experience, indicate that those de- 
grees are produced by e<|ual increments of 
the matter of heat, or caloric ; but then it 
should be understood they are to be applied 
to a body of uniform bulk and capacity, such 
as air confined within a given space. If 
water, fof instance, in its ordinary state, is to 
be raised successively through equal intervals of 
temperature, as measured by this scale, thea 
unequal increments of heat will be requisite, 
by reason of its increased capacity. The first 
number in the column, — 175", denotes the 
point at which mercury freezes, hitherto mark- 
ed — 40°. The calculations are made for every 
10° from — 68° to 212"; above the last num- 
ber, for every 100°. By comparing this column 
with the 5th, the correspondences of the new 
scale and the common one are perceived : the 
greatest difference between S2° and 212° is 
observable at 122° of the new scale, which 
agrees with 110' of the old, the diflference 


being 12° ; but below 32° and above 212% the 
differences become more remarkable. 

The 2d and 3d columns are two series, the 
one of roots, and the other of their squares. 
They are obtained thus ; opposite 32°, in the 
first column, is placed in the 3d, 72°, being 
the number of degrees or equal parts in Fahren- 
heit's scale from freezing mercury to freezing 
water ; and opposite 2 1 2° in the first is placed 
252° in the 3d, being 212 + 40°, the number 
of degrees (or rather equal parts) between 
freezing mercury and boiling water. The 
square roots of these two numbers, 72" and 
252°, are found and placed opposite to them 
in the second column. The number 8.4853 
represents the relative quantity of real tem- 
perature between freezing mercury and free- 
zing water; and the number 15.8743 repre- 
sents the like between freezing mercury and 
boiling water ; consequently the difference 
7.3890 represents the relative quantity between 
freezing water and boiling water, and 7.3890 
-^ 18 =.4 105 represents the quantity corres- 
ponding to each interval of 10°. By adding 
.4105 successively to 8.4853, or subtracting it 
from it, the rest of the numbers in the column 
are obtained, which are of course in arithme- 
tical progression. The numbers in the 3d 
column arc all obtained by squaring those of 


the 2d opposite to them. The unequal dif- 
ferences in the 3d column mark the expansions 
of mercury due to equal increments of tem- 
perature, by the theory. The inconvenient 
length of the table prevents its being carried 
down by ifitervals of 10" to the point of free- 
zing mercury, which however is found to be 
at —175°. 

The 4th column is the same as the 5d, with 
the difference of 40°, to make it conform to 
the common method of numbering on Fahren- 
heit's scale. 

The 5th column is the 4th corrected, on 

account of the unequal expansion of Glass : — 

The apparent expansion of mercury in glass 

is less than the real, by the expansion of the 

glass itself; this, however, would not disturb the 

law of expansion of the liquid, both apparent 

and real being subject to the same, provided 

the glass expands equally ; this will be shewn 

hereafter. But it has been shewn by De 

Luc, that glass expands less in the lower 

half of the scale than the higher ; this must 

occasion the mercury apparently to expand 

more in the lower half than what is dictated 

by the law of expansion. By calculating 

from De Luc's data, I find, that the mercury 

in the middle of the scale, or 122°, ought to be 

found nearly 3° higher than would be, were it 


not for this increase. Not however to over-rate 
the effect, I have taken it only at r.7, making 
the number 108% 3 in the 4th column, 110° 
in the 5th, and the rest of the column is cor- 
rected accordingly. The numbers in this 
column cannot well be extended much beyond 
the interval from freezing to boiling water, for 
want of experiments on the expansion of glass. 
By viewing this column along with the 1st, the 
quantity of the supposed error in the common 
scale may be perceived ; and any observations 
on the old thermometer may be reduced to 
the new. 

The 6th column contains the squares of the 
natural series 1, 2, 3, &c. representing the 
expansion of water by equal intervals of tem- 
perature. Thus, if a portion of water at 
42" expands a quantity represented by 289, at 
the boiling temperature, then at 52° it will be 
found to have expanded I, at 62°, 4 parts, &c. 
&c. Water expands by cold or the abstrac- 
tion of heat in the same way below the point 
of greatest density, as will be illustrated when 
we come to consider the absolute expansion of 
bodies. The apparent greatest density too 
does not happen at 39°,3 old scale ; but about 
42° ; and the greatest real density is at or near 
36° of the same. 

The 7th column contains a series of num- 


bers in Geometrical Progression, denoting the 
expansion of air, or elastic fluids. The volume 
at 32' is taken 1000, and at 212% 1376 accord- 
ing to Gay Lussac's and my own experiments. 
As for the expansion at intermediate degrees. 
General Roi makes the temperature at mid- 
way of total expansion, 1 I6°i old scale ; from 
the results of ray former experiments, (Manch. 
Mem. Vol. 5, Part 2, page 599) the tem- 
perature may be estimated at 1 19°4 ; but I had 
not then an opportunity of having air at 32% 
By more recent experiments T am convinced 
that dry air of 32' will expand the same qiian- 
tity from that to 117° or 118° of common scale, 
as from the last term to 212°. According to 
the theory in the above Table it appears, that 
air of 117° will be 1188, or have acquired one 
half its total expansion. Now if the theory ac- 
cord so well with experiment in the middle of 
the interval, we cannot expect it to do other- 
wise in the intermediate points. 

The 8th column contains the force of aque- 
ous vapours in contact with water expressed 
in inches of mercury, at the respective tem- 
peratures. It constitutes a geometrical pro- 
gression; the numbers opposite 32° and 212°, 
namely, .200 and 30.0 are derived from ex- 
periments, (ibid, page 559) and the rest are 
determined from theory. It is remarkable that 


those numbers do not differ from the table 
just referred to, which was the result of ac- 
tual experience, so much as 2° in any part; a 
difference that might even exist between two 
thermometers of the same kind. 

The 9th column exhibits the force of the 
vapour of sulphuric ether in contact with 
liquid ether ; which is a geometrical progres- 
sion, having a less ratio than that of water. 
Since writing my former Essay on the Force 
of Steam, I am enabled to correct one of the 
conclusions therein contained ; the error was 
committed by trusting to the accuracy of the 
common mercurial thermometer. Experience 
confirmed me that the force of vapour from 
water of nearly 2 1 2% varied from a change of 
temperature as much as vapour from ether of 
nearly 100°. Hence I deduced this general 
Jaw, namely, " that the variation of the force 
of vapour from all liquids is the same for the 
same variation of temperature, reckoning from 
vapour of any given force." — But I now find 
that 30° of temperature in the lower part of 
the common scale is much more than 30° in 
the higher: and therefore the vapours of ether 
and water are not subject to the same change 
of force by equal increments of temperature. 
The truth is, vapour from water, ether and 
other liquids, increases in force in geometri- 


cal progression to the temperature; but the 
ratio is different in different fluids. Ether as 
manufactured in the large way, appears to be 
a very homogeneous liquid. I have purchased 
it in London, Edinburgh, Glasgow and Man- 
chester, at very different times, of precisely the 
same quality in respect to its vapour ; namely, 
such as when thrown up into a barometer 
would depress the mercury 15 inches at the 
temperature of 68°. Nor does it lose any of 
its effect by time ; I have now a barometer 
with a few drops of ether on the mercury, that 
has continued with invaried efBcacy for eight 
or nine years. The numbers in the column 
between the temperatures of 20° and 80°, are 
the results of repeated observations on the 
above ether barometer for many years ; those 
above and beloW are obtained from direct 
experiment as far as from to 212° ; the low 
ones were found by subjecting the vacuum of 
the barometer to an artificial cold mixture ; 
and the higher ones were found in the manner 
related in my former Essays : only the highest 
force has been considerably increased from 
what I formerly had it, in consequence of 
supplying the manometer with more ether i 
it having been found to leave little or no liquid 
when at the temperature of 212° ; and in order 
to obtain the maximum effect it is indispen- 


sible to have a portion of liquid remaining 
in contact with the vapour. 

The 10th column shews the force of va- 
pour from alcohol, or rather common spirit of 
wine, determined by experiment in the same 
way as the vapour of water. This is not a 
geometrical progression, probably because the 
liquid is not pure and homogeneous. I sus- 
pect the elastic fluid in this case is a mixture 
of aqueous and alcoholic vapour* 



One important effect of heat is the expan- 
sion of bodies of every kind. Solids are least 
expanded ; liquids more ; and elastic fluids 
most of all. The quantities of increase in 
bulk have in many instances been determined; 
but partly through the want of a proper ther- 
mometer, little general information has been 
derived from particular experiments. The 
force necessary to counteract the expansion 
has not been ascertained, except in the case 
of elastic fluids s but there is no doubt it is 
very great. The quantity and law of expan- 
sion of all pernianeBt elastic fluids have alreadjr 


bcen'given ; it remains then to advert to liquid 
and solid bodies. 

In order to understand the expansion of 
liquids, it is expedient to premise certain 
propositions : 

1st. Suppose a thermometrical vessel of glass, 
metal, &c., were filled with any liquid up to 
a certain mark in the stem ; and that it was 
known the vessel and the liquid had precisely 
the same expansion, bulk for bulk, with the 
same change of temperature ; then it must be 
evident upon a little consideration, that what- 
ever change of temperature took place, the 
liquid must remain at the same mark. 

2. Suppose as before, except that both 
bodies expand uniformly with the tempera- 
ture, but the liquid at a greater rate than the 
vessel ; then it is evident by an increase of 
temperature, the liquid w^ould appear to ascend 
uniformly a quantity equal to the difference 
of the absolute expansion of the two bodies. 

3. Suppose as in the last case, but that Ihe li- 
quid expands at a less rate than the vessel ; the 
liquid would then descend, and that uniformly 
by an increase of temperature, a quantity equal 
to the difference of the absolute expansions. 

4. Suppose as before, only the vessel now 
expands uniformly, and the liquid with a ve- 
locity uniformly accelerated, commencing from 


rest ; in this case if temperature be added 
uniformly, the liquid will appear to descend 
with a velocity uniformly retarded to a certain 
point, there to be stationary, and afterwards to 
ascend with an uniformly accelerated velocity, 
of the same sort as the former. — For, as 
the velocity with which the liquid expands is 
unifornrly accelerative, it must successively pass 
through all degrees from to any assigned 
quantity, and must therefore in some mo- 
ment be the same as that of the vessel, and 
therefore, for that moment, the liquid must ap- 
pear stationary : previously to that time the 
liquid must have descended by the third pro- 
position, and must afterwards ascend, by the 
2d. but not uniformly. Let the absolute 
space expanded by the liquid at the moment 
of equal velocities be denoted by 1, then that 
of the vessel in the same time must be 2 j be- 
cause the velocity acquired by an uniformly 
accelerating force, is such as to move a body 
through twice the space in the same time. It 
follows then that the liquid must have sunk 
1, being the excess of the expansion of the 
vessel above that of the liquid. Again, let 
another portion of temperature equal to the 
former be added, then the absolute expansion 
of the liquid will be 4, reckoned from the com- 
mencement J and the expansion of the vessel 


also 4 : the place of the liquid will be the same 
as at first, and therefore it must apDarently 
ascend 1 by the 2d portion. Let a third por- 
tion of heat equal to one of the former be 
added, and it will make the total expansion 
of the liquid 9, or give 5 additional expan- 
sion, from which deducting 2, that of the 
vessel, there remains 3 for the apparent ex- 
pansion by the 3d portion ; in like manner 5 
will be due for the 4th, and 7 for the 5th, &c., 
being the series of odd numbers. But the 
aggregate of these forms a series of squares, 
as is well known. Hence the apparent expan- 
sion will proceed by the same law as the real, 
only starting from a higher temperature. If 
the law of expansion of the liquid be such 
that either the addition or abstraction of tem- 
perature, that is, either heat or cold produces 
expansion alike, reckoned from the point of 
greatest density j then the apparent expansion 
will still be guided by the same law as the 
real. For^ if when the liquid is at the lowest 
point of the scale, we withdraw a portion of 
heat, it ascends to 1 ; or is in the circumstance 
of greatest density, and no expansion as at 
the commencement; if then we withdraw 
another portion, it will expand 1 by hypothe- 
sis, but the vessel will contract 2, which must 
make the apparent expansion o£ the liquid 3 ; 


by another portion it will be 5, by another 7, 
&c., as before. 

The truth of the above proposition may be 
otherwise shewn thus : 

Let 1, 4, 9, 16, 25, &c., represent the ab- 
solute expansions of the liquid, and /), 2 p, 
3 p, 4 /?, 5 /;, &c., those of the vessel by 
equal increments of temperature, then 1 — •/?, 
4— 2p, 9—3/7, 16—4/7, 25 — 5 p, &c., will 
represent the apparent expansion of the li- 
quid ; the differences of these last quantities, 
namely 3 — /;, 5 — p, 7 — p^ 9 — p, &c., form 
a series in arithmetical progression, the com- 
mon difference of which is 2. But it is de- 
monstrated by algebraists, that the differences 
of a series of square numbers, whose roots are 
in arithmetical .progression, form an arithme- 
tical progression, and that the common differ- 
ence of the terms of this progression is equal 
to twice the square of the difference of the 
roots. Hence, as 2 = twice the square of 1, 
we have the above arithmetical series 3 — p, 
5—/), &c., equal to the differences of a series 
cf squares, the common difference of the roots 
of which is 1. 

Now to apply these principles : solid bodies 
are generally allowed to expand uniformly 
within the common range of temperature : at 
all events the quantity is so small compared 


with the expansion of liquids, such as water,that 
the deviation from uniformity cannot require 
notice in many cases. Water being supposed 
to expand according to the square of the tem- 
perature from that of greatest density, we may 
derive the following conclusions. 

Cor. 1. The laws of uniformly accele- 
rated motion, are the same as those of the 
expansion of water, whether absolute or appa- 
rent, the time in one denoting the temperature 
in the other, and the space denoting the ex- 
pansion : that is, if ^ = time or temperature, 
V = velocity, and s = space or expansion : 

/% or tvj or v^ are as s. 

i tV:^ s 
V IS as t 

j- is as 2 ^ ^ 

s is as tf t being supposed constant, &c. 

Cor. 2. The real expansion of water 
from maximum density for any number of de- 
grees of temperature, is the same as the ap- 
parent expansion from apparent greatest den- 
sity in any vessel for the same number of 
degrees. For instance, if water in a glass 
vessel appears to be of greatest density, or 
descends lowest at 42° of common scale, and ap- 
pears to expand iV of its first volume from thenct 


to 212° ; then it may be inferred that the real 
expansion of water from greatest density by 
170° is Vt o^ i^s volume ; so that the absolute 
expansion of water is determinable this way, 
without knowing either at what temperature 
its density is greatest, or the expansion of the 
vessel containing it. 

Cor. 3. If the expansion of any vessel 
can be obtained; then may the temperature 
at which water is of greatest density be ob- 
tained ; and vice versa. This furnishes us 
with an excellent method of ascertaining both 
the relative and absolute expansion of all 
solid bodies that can be formed into vessels 
Cc.pable of holding water. 

Cor. 4. If the apparent expansion of water 
from maximum density for 180° were to be 
equalled by a body expanding uniformly, its 
velocity must be equal to that of water at 90% 
or mid-way. — And if any solid body be found 
to have the same expansion as water at 10* 
from max. density; then its expansion for 180* 
must be ^ of that of water, &;c. Because in 
water v is as t^ &c. 

By graduating several glass thermometer 
vessels, filling them with water, exposing 
them to different temperatures, and comparing 
results, I have found the apparent expansion 
of water in glass for every 10° of the common 



or old scale (as I shall henceforward call it) 
and the new one, as under. 



























100083 I 




100180 1 












100672 j 




100880 j 




1011 16 









































The whole expansion of water for 1 80° of 
temperature, reckoned from the point of great- 
est density, appears from the 2d Table to be 

T.-5-, or 214 parts become 224. 

In the Edinburgh Philosophical Transactions 



for 1804, Dr. Hope has given a paper on tlie 
contraction of water by heat in low tempera- 
tures. (See also Nicholson's Journal, Vol. 12.) 
Jn this paper we find an excellent history of 
facts and opinions relative to this remarkable 
question in physics, with original experiments. 
Tliere appear to have been two opinions res- 
pecting the temperature at which water obtains 
its maximum density ; the one stating it to 
be at the freezing point, or 32° ; the other at 
40°. Previously to the publication of the above 
essay, I had embraced the opinion that the 
point was S2°, chiefly from some experiments 
about to be related. Dr. Hope argued from 
his own experiments in favour of the other 
opinion. IMy attention was again turned 
to the subject, and upon re-examination 
of facts, I found them all to concur in giving 
the point of greatest density at the temperature 
56", or mid-way between the points formerly 
supposed. In two letters inserted in Nichol- 
son's Journal, Vol. 13 and 14, I endeavour- 
ed to shew that Dr. Hope's experiments 
supported this conclusion and no other. I 
shall now shew that my own experiments on 
the apparent expansion of water in different 
vessels, coincide with them in establishing the 
same conclusion. 

The results of my experiments, without 


those deductions, were published in Nichol- 
son's Journal, Vol. 10. Since then some small 
additions and corrections have been made. 
It may be observed that small vessels, capable 
of holding one or two ounces of water, were 
made of the different materials, and such as 
that glass tubes could be cemented into them 
when full of water, so as to resemble and act 
as a common thermometer. The observations 
follow : 

Water it»tionary. Con eeponding points 
of expansion. 

1 Brown earthen ware »t 38« at 32° & 44« 

2 Common white ware, and 7 ^,^ ^^ & 48 -f 

stone ware, 3 

3 Flint glass 42 32 8c 521 

4 Iron 42-1- 32 & 53— 

5 Copper 45-|- 32 & 59 

6 Brass 4-5| 02 & 60— 

7 Pewter 4-6 32 & 60f 

8 Zinc 48 32 & 64+ 

9 Lead 49 32 & 67 

As the expansion of earthen ware by heat 
has never before been ascertained, we cannot 
make use of the first and second experiments 
to find the temperature of greatest density ; all 
that we can learn from them is, that the point 
must be below 38°. 

According to Smeaton, glass expands ttW 
in length for 180° of temperature ; consequent- 
ly it expands -^^ in bulk. But water expands 



^,7- or rather more than 1 8 times as much ; 
theretore the mean velocity of the expansion 
of water (which is that at 90% or half way) is 
18 times more than that of glass, which is 
equal to the expansion of water at 42° ; this 
last must therefore be -^-^ of the former ; con- 
sequently water of 42° has passed through 
tV of the temperature to the mean, or -t^ of 
90° = 5°, of new scale = 4° of old scale, above 
the temperature at which it is absolutely of 
greatest density. This conclusion however 
cannot be accurate ; for, it appears from the 
preceding paragraph that the temperature 
must be below 38°. The inaccuracy arises, I 
have no doubt, from the expansion of glass 
having been under-rated by Smeaton ; not from 
any mistake of his, but from the peculiar 
nature of glass. Rods and tubes of glass are 
seldom if ever properly annealed ; hence they 
are in a state of violent energy, and often 
break spontaneously or with a slight scratch 
of a file : tubes have been found to expand 
more than rods, and it might be expected that 
thin bulbs should expand more still, because 
they do not require annealing ; hence too the 
great strength of thin glass, its being less brit- 
tle, and more susceptible of sudden transitions 
of temperature. From the above experiments 
it seems that the expansion due to glass, such 


as the bulbs of ordinary thermometers, is very 
little less than that of iron. 

Iron expands nearly ^4t5- in length by 18Cr 
of heat, or TFT in bulk ; this is nearly ^V of 
the expansion of water; hence 90 -r- 12 = 7'§ 
of true mean temperature = 6" of common 
scale; this taken from 42°+, leaves 36° of 
common scale for the temperature at which 
water is of greatest density. 

Copper is to iron as 3 ^ 2 in expansion; 
therefore if 6° be the allowance for iron, that 
for copper must be 9° ; hence 45°~ 9° = 36°, 
for the temperature as before. 

Brass expands about ,V more than copper j 
hence we shall have 4-5°l — 9°l = 36°, for the 
temperature as above. 

Fine pewter is to iron as 1 1 : 6 in expan- 
sion, according to Smeaton ; hence 46° — 
11°= 35°^ for the temperature as derived from 
the vessel of pewter : but this being a mixed 
metal, it is not so much to be relied upon. 

Zinc expands TIT in bulk for 180°, if we 
may credit Smeaton : hence water expands 5^ 
times as much as zinc ; and 90 -^ 5i- = 17° of 
new scale = 13°^ of old scale ; whence 48° — 
13°-| = 34°1 for the temperature derived from 
zinc. It seems highly probable that in ibis 
case the expansion of the vessel is over-rated ; 
it was found to be less than that of lead, 


whereas Smeaton makes it more. The vessel 
was made of the patent malleable zinc of Hod- 
son and Sylvester. Perhaps it contains a por- 
tion of tin, which will account for the devia- 

Lead expands ^^-^ of its bulk for 180°; 
water therefore expands about 5$ times as 
much ; this gives 90 -^ 51 = 16°! of new scale 
= 13° of old scale ; whence 49* — 13° = 36% 
as before. 

From these experiments it seems demon- 
strated, that the greatest density of water is 
at or near the 36° of the old scale, and 37° or 
38° of the new scale : and further, that the 
expansion of thin glass is nearly the same as 
that of iron, whilst that of stone ware is y, 
and brown earthen ware ^ of the same. 

The apparent expansion of mercury in a 
thermometrical glass for 180* I find to be .0163 
from 1. That of thin glass may be stated at 
.0037 = ir^, which is rather less than iron, 
^<.^. Consequently the real expansion of mer- 
cury from 32° to 212° is equal to the sum of 
these = .02 or -^. DeLuc makes it, .01836, 
and most other authors make it less ; because 
they have all under-rated the expansion of 
glass. Hence we derive this proportion, 
0163 : 180° :: .0037 : 41° nearly, which ex- 
presses the effect of the expansion of glass on 


the mercurial thermometer : that is, the mer- 
cury would rise 41° higher on the scale 
at the temperature of boiling water, if the 
glass had no expansion. — De Luc makes the 
expansion of a glass tube from 32° to 212° = 
.00083 in length, and from 32=" to 122° only 
.00035. This inequality arises in part at least, 
I apprehend, from the want of equilibrium in 
the original fixation of glass tubes, the outside 
being hard when the inside is soft. 

Liquids may be denominated pure when 
they are not decomposed by heat and cold. 
Solutions of salts in water cannot be deemed 
such ; because their constitution is affected by 
temperature. Thus, if a solution of sulphate 
of soda in water be cooled, a portion of the 
salt crystallizes, and leaves the remaining liquid 
less saline than before; whereas water and 
mercury, when partially congealed, leave the 
remaining liquid of the same quality as before. 
Most acid liquids are similar to saline solutions 
in this respect. Alcohol as we commonly 
have it, is a solution of pure alcohol in a 
greater or less portion of water : and probably 
would be affected by congelation like other 
solutions. Ether is one of the purest liquids, 
except water and mercury. Oils, both fixed 
and volatile, are probably for the most part 
impure, in the sense we use it. Notwithstand- 


ing these observations, it is remarkable how 
nearly those liquids approximate to the law of 
expansion observed in water and mercury. 
Few authors have made experiments on these 
subjects; and their results in several instances 
are incorrect. My own investigations have 
been chiefly directed to water and mercury ; 
but it may be proper to give the results of my 
enquiries on the other liquids as far as they 
have been prosecuted. 

Alcohol expands about ^ of its bulk for 
180**, from — 8 to 172°. The relative expan- 
sions of this liquid are given by De Luc 
from 32" to 212°; but the results of my expe- 
riments do not seem to accord with his. Ac- 
cording to him alcohol expands 35 parts for 
the first 90°, and 45 parts for the second 90". 
The strength of his alcohol was such as to fire 
gun-powder : but this is an indefinite test. 
From my experiments I judge it must have 
been very weak. I find 1000 parts of alcohol 
of .817 sp. gravity at the temperature 50° be- 
came 1079 at the temperature 170° of the 
common mercurial scale : at 110° the alcohol 
is at 1039, or balf a division below the true 
mean. AVhen the sp. gravity is .86, 1 find 1000 
parts at 50° become 1072 at 170° ; at 110' the 
bulk is 1035 +, whence the disproportion of 
the two parts of the scale is not so much 


in this case as 35 to 37. When the sp. 
gravity is ,937, I find 1000 parts become 
1062 at 170", and 10291 at llO^j hence the 
ratio of the expansion becomes 291 to 321. 
When the sp. gravity is ,967, answering to 75 
per cent, water, I find 1000 parts at 50* be- 
come 1040 at 170% and 10171 at 110°, giving 
a ratio of 35 to 45 ; which is the same as De; 
Luc gives for alcohol. It is true he takes an 
interval of temperature =x 180% and I take one 
for 120* only j but still it is impossible to re- 
concile our results. As the expansion of alco- 
hol from 172' to 212° must have been con- 
jectural, perhaps be has over-rated it. In 
reporting these results I have not taken into 
account the expansion of the glass vessel, a 
large thermometrical bulb, containing about 
750 grains of water, and having a tube pro- 
portionally wide J consequently the real ex- 
pansions must be considered as more rather 
than less than above stated. The graduation 
of the vessel having been repeatedly examined, 
and being the same that was used in deter- 
mining the expansion of water, I can place 
confidence in the results. Particular care was 
taken in these experiments to have the bulb 
and stem both immersed in water of the pro- 
posed temperature. 

As alcohol of .817 sp. gravity contains at 


least 8 per cent, water, it is fair to infer from 
the above that a thermometer of pure alcohol 
would in no apparent degree differ from one 
of mercury in the interval of temperature from 
SO** to 170*. But when we consider that the 
relative expansions of glass, mercury and alco- 
hol for this interval, are as 1,52 and 22 re- 
spectively, it must be obvious that the inequa- 
lity of the expansion of glass in the higher 
and lower parts of the scale, which tends to 
equalise the apparent expansion of mercury, 
has little influence on alcohol, by reason of its 
comparative insignificance. Hence it may be 
presumed that a spirit thermometer would be 
more equable in its divisions than a mercu- 
rial one, in a vessel of uniform expansion. 
This it ought to be by theory, because the 
point of greatest density or congelation of 
alcohol is below that of mercury. 

Water being densest at 36°, and alcohol at 
a very remote temperature below, it was to 
be expected that mixtures of these would be 
densest at intermediate temperatures, and those 
higher as the water prevailed j thus we find the 
disproportion, so observable in the expansion 
of water, growing greater and greater in the 
mixtures as they approach to pure water. 

Water saturated with common salt expands 
as follows : 1000 parts at 32° become 1050 


at 212*; at 122° it is nearly 1023, which 
gives the ratio of 23 to 27 for the correspond- 
ing equal intervals of mercury. This is 
nearly the same as De Luc's ratio of 36. S to 
43.7. This solution is said to congeal at — 7°, 
and probably expands nearly as the square of 
the temperature from that point. It differs 
from most other saline solutions in regard to 
its expansion by temperature. 

Olive and linseed oils expand about 8 per 
cent, by 180° of temperature ; De Luc finds 
the expansion of olive oil nearly correspond 
to mercury ; with me it is more disproportion- 
ate, nearly agreeing with water saturated with 

Oil of turpentine expands about 7 per cent, 
for 180° j it expands much more in the higher 
than in the lower part of the scale, as it ought to 
do, the freezing point being stated at 14 or 
16°. The ratio is somewhere about 3 to 5. 
Several authors have it that oil of turpentine 
boils at 560° J I do not know how the mis- 
take originated; but it boils below 212°, like 
the rest of the essential oils. 

Sulphuric acid, sp. gravity K85 expands 
about 6 per cent, from 32° to 212°. It accords 
with mercury as nearly as possible in every 
part of the scale. Dr. Thomson says the 
freezing point of acid of this strength is at 


—36° or below j whence it accords with the 
same law as water and mercury. I find that 
even the glacial sulphuric acid, or that of 
1.78 sp. gravity, which remains congealed at 
45°, expands uniformly, or nearly like the 
other, whilst it continues liquid. 

Nitric acid, sp. gravity 1.40, expands about 
11 per cent, from 32° to 212°; the expansion 
is nearly of the same rate as that of mercury, 
the disproportion not being more than 27 to 
28 or thereabouts. The freezing point of acid 
of this strength is near the freezing point of 

Muriatic acid, sp. gravity 1.137, expands 
about 6 per cent, from 32° to 212°; it is 
more disproportionate than nitric acid, as 
might be expected, being so largely diluted 
with water. The ratio is nearly 6 to 7. 

Sulphuric ether expands after the rate of 
7 per cent, for 180° of temperature. I have 
only compared the expansion of this liquid 
with that of mercury from 60° to 90^ In 
this interval it accords so nearly with mercury 
that I could perceive no sensible difference in 
their rates. It is said to freeze at — 46°. 

From what has been observed it may be 
seen that water expands less than most other 
liquids ; yet it ought to be considered as hav- 
ing in reality the greatest rate of expansion. 


Alcohol and nitric acid, which appear to ex- 
pand so much, do not excel, or even equal 
water, if we estimate their expansion from, 
the temperature of greatest density, and com- 
pare them with water in like circumstances. 
It is because we begin with them at 100 or 200* 
above the point of greatest density, and ob- 
serve their expansion for 180° further, that 
they appear to expand so largely. Water, if it 
continued liquid, would expand three times 
as much in the second interval of 180" as it 
does in the first, reckoning from 36°, 


No general law has hitherto been discovered 
respecting the expansion of solid bodies ; but 
as elastic fluids and liquids appear to be sub- 
ject to their respective laws in this paxticular, 
we may confidently expect that solids will be 
found so too. As it may be presumed tnat 
•olids undergo no change of form, by the ab- 
straction of heat, it is probable that whatever 
the law may be, it will respect the point at 
wiiich temperature commences, or what may 
be called, absolute cold. It is not our pr£- 
lent business to enquire how low this point is ', 
but it may be observed that every phenomenoB 


indicates it to be very low, or much lower 
than is commonly apprehended. Perhaps it 
may hereafter be demonstrated that the inter- 
val of temperature from 32° to 212* of Fahren- 
heit, constitutes the 10th, 1 5th, or 20th inter- 
val from absolute cold. Judging from analogy, 
we may conjecture that the expansion of solids 
is progressively increasing with the tempera- 
ture ; but whether it is a geometrical progres- 
sion as elastic fluids, or one increasing as the 
square of the temperature, like liquids, or as 
the 3d or any power of the temperature, still 
if it be estimated from absolute cold, it must 
appear to be nearly uniform, or in arithmetical 
progression to the temperature, for so small 
and remote an interval of temperature as 
that between freezing and boiling water. The 
truth of this observation will appear from the 
following calculation : let us suppose the inter- 
val in question to be the 15th ; then the real 
temperature of freezing water will be 2520 , 
the mid-way to boiling 2610% and boiling 
water 2700% reckoned from absolute cold. 

TO* = 196 

— 14|. 

T4j^* = 210f 
17^* = 225 


14^' = 2744 


rip 3 = 3048| 


l7l» = 3375 


Now the differences above represent the 
ratios of expansion for 90° of temperature ; 
they are in the former case as 57 to 59, and in 
the latter as 14 to iS nearly. Bat the tem- 
perature being supposed to be measured by 
the new scale, the mean is about 110° of the 
old scale ; therefore the expansion of solids 
should be as 57 or 14 from 32° to 1 10°, and as 
59 or 15 from 110° to 212° of the old scale. 
If these conjectures be right, the expansion of 
solids ought to be something greater in the low- 
er part of the old scale, and something less in 
the higher part. Experience at present does 
not enable us to decide the question. For all 
practical purposes we may adopt the notion of 
the equable expansion of solids. Only glass 
has been found to expand increasingly with the 
temperature, and this arises probably from its 
peculiar constitution, as has been already ob- 

Various pyrometers, or instruments for mea- 
suring the expansion of solids, have been in- 
vented, of which accounts may be seen in 
books of natural philosophy. Their object is 
to ascertain the expansion in length of any 
proposed subject. The longitudinal expansion 
being found, that of the bulk may be derived 
from it, and will be three times as much. 
Thus, if a bar of 1000 expand to 1001 by a 



certain temperature ; then 1000 cubic inches 
of the same will become 1003 by the same 

The following Table exhibits the expansion 
of the principal subjects hitherto determined, 
for 180° of temperature; that is, from 32° to 
212° of Fahrenheit. The bulk and length of 
the articles at 32° are denoted by 1. 



Brown earthen ware...... 

Stooft ware - 

Glass — rod J and tubps 

bulbs (thin) 

Platinum .............. 




Bismuth . ... 

Cnppi-r ........ 

Brass , 

Silvrr -..--...., 

Fine Pewter 


lu bulk. 

,0023 = 



.co;i7 = j|^ 



0051 = ,^^ 
.007 1- 

Lead \ .0086=_J. 



Mercury . . . 


Water sat. wiili salt 

Sulphuric acid . 

Muriatic Acid 

Oil of turpentine.. 


Fixed oils 


Nitric acid ....... 




In length, 




TjTT + 

T5T t 




Cases of all kinds.. 

0093 =,i^ 

•0200 =^»y 
.04-66 =-jV..Y 
.0500 =J^ 

.0600 =.rV 
.0600 =/,. 

.0110= ^ 

0110= J 












.376 = I 

•)• Smcaton, * "Ellicott. % Borda. 


Wedgwood's Thermometer. 

The spirit thermometer serves to measure 
the greatest degrees of cold we are acquainted 
with, and the mercurial thermometer measures 
400° above boiling water, by the old scale, or 
about 250° by the new one, at which tempera- 
ture the mercury boils. This is short of red 
heat, and very far short of the highest attain- 
able temperature. An instrument to measure 
high temperatures is very desirable ; and Mr. 
Wedgwood's is the best we have yet ; but 
there is still great room for improvement. 
Small cylindrical pieces of clay, composed in 
the manner of earthen ware, and slightly 
baked, are the thermometrical pieces. When 
used, one of them is exposed in a crucible to 
the heat proposed to be measured, and after 
cooling, it is found to be contracted, in pro- 
portion to the heat previously sustained ; the 
quantity of contraction being measured, indi- 
cates the temperature. The whole range of 
this thermometer is divided into 240 equal 
degrees, each of which is calculated to be 
equal to 130° of Fahrenheit. The lowest, or 0, 
isfoundabout 1077°of Fahrenheit (supposing the 
common scale continued above boiling mer- 
cury,) and the highest 32277°. According to 
the nevv views of temperature in the preceding 

45 out EX FANS 10 V. 

pages, there is reason to think these numbers 
are much too large. 

The following Table exhibits some of the 
more remarkable temperatures in the whole 
range, according to the present state of our 


Extremity of Wedgwood*s thermometer...., 2i0* 

Pig iron, cobalt and nickel, melt from 130' to...... 150 

Greatest beat of a Smith's forge 125 

Furnaces for glass and earthen ware, from 40 to 124 

Gold melts 32 

Settling heat of flint glass 29 

Silver melts 28 

Copper melts .^ 27 

Brass melts 21 

Diamond burns 14 

Red heat risible in day-light 


old scale. 

Hydrogen and charcoal burn 800° to 1000® 

Antimony melts 809 

Zinc 700 

Lead 612 

Mercury boils 600 

Linseed oil boils 600 

Sulphuric acid boils 590 

Bismuth... 476 

Tin 442 

Sulphur burns slowly 30^ 

Nitric acid boils 240 

Water and essential oils boil 213 

^ismutk 5 parts, tia 3 and lead 2, melt ....#,. 210 



Alcohol boils 174» 

Beeswax melts 142 

Ether boils. 98 

Blood heat 96« to 98 

Summer heat in this climate 75" to.............. 80 

Sulphuric acid (1 .78) when congealed, begins to melt 45 

Mixtureof ice and water .............. 32 

Milk freezes 50 

Vinegar freezes — 28 

Strong wines freeze about.... ......... — . 20 

Snow 3 parts, salt2....... — ................ — 7 

Cold observed on the snow at Kendal, 179 1...... — tO 

Pitto at Glasgow, 1780 — 23 

Mercury freezes .. — ................ — 39 

Createst artificial cold observed —90 




If the whole quantity of heat in a mcasate 
of water of a certain temperature be denoted 
by 1, that in the same measure of mercury will 
be denoted by .5 nearly : hence the specific 
heats of water and mercury, of equal bulks, 
may be signified by 1 and .5 respectively. 

If the specific heats be taken from equal 
heights of the two liquids ; then they will be 


denoted by 1 and .04 nearly j because we 
have to divide .5 by 13.6, the specific gravity 
of mercury. 

That bodies differ much in their specific 
heats, is manifest from the following facts. 

1. If a measure of mercury of 212* be 
mixed with a measure of water of 32", tbo 
mixture will be far below the mean tempera- 

2. If a measure of mercury of 32° be mix- 
ed with a measure of water of 212% the 
mixture will be far above the mean. 

3. If two equal and like vessels be filled, 
the one with hot water, the other with hot 
mercury ; the latter will cool in about half 
the time of the former. 

4. If a measure of sulphuric acid be mixed 
with a measure of water of the same tempe- 
rature, the mixture will assume a temperature 
about 240° higher. 

These facts clearly shew that bodies have 
various affinities for heat, and that those bodies 
which have the strongest attraction or affinity 
for heat, possess the most of it in like circum- 
stances ; in other words, they are said to have 
the greatest capacity for heat, or the greatest 
specihc heat. It is found too that the same 
body changes its capacity for heat, or appa- 
rently assumes a new affinity, with a change of 


form. This no doubt arises from a new 
arrangement or disposition of its ultimate par- 
ticles, by which their atmospheres of heat are 
influenced : Thus a solid body, as ice, on be- 
coming liquid, acquires a larger capacity for 
heat, even though its bulk is diminished ; and 
a liquid, as water, acquires a larger capacity 
for heat on being converted into an elastic 
fluid ; this last increase is occasioned, we may 
conceive, solely by its being increased in 
bulk, in consequence of which every atom of 
liquid possesses a larger sphere than before. 

A very important enquiry is, whether the 
same body in the same state undergoes any 
change of capacity by change of temperature. 
Does water, for instance, at 32° possess the 
same capacity for heat, as at 212% and through 
all the intermediate degrees ? Dr. Crawford, 
and most writers after him, contend, that the 
capacities of bodies in such circumstances are 
nearly permanent. As an outline of doctrine 
this may be admitted ; but it is requisite, if 
possible, to ascertain, whether the small change 
of capacity induced by temperature, is such as 
to increase the capacity, or to diminish it ; and 
also, whether the increase or diminution is 
uniform or otherwise. Till this point is settled, 
it is of little use to mix water of 32° and 212°> 


with a view to obtain the true mean tempera- 

That water increases in its capacity for heat 
with the increase of temperature, I consider 
demonstrable from the following arguments : 
1st. A measure of water of any one tempera- 
ture being mixed with a measure at any other 
temperature, the mixture is less than two 
measures. Now a condensation of volume 
is a certain mark of diminution of capacity 
and increase of temperature, whether the con- 
densation be the effect of chemical agency, as 
in the mixture of sulphuric acid and water, 
or the effect of mechanical pressure, as with 
elastic fluids. 2. When the same body sud- 
denly changes its capacity by a change of form, 
it is always from a less to a greater^ as the 
temperature ascends ; for instance, ice, water 
and vapour. 3. Dr. Crawford acknowledges 
from his own experience, that dilute sulphuric 
acid, and most other liquids he tried, wer« 
found to increase in their capacity for heat with 
the increase of temperature. 

Admitting the force of these arguments, it 
follows that when water of 52' and 212" are 
mixed, and give a temperature denoted by 
119" of the common thermometer, we must 
conclude that the true mean temperature is 
somewhere below that degree. I have already 


assigned the reasons why I place the mean at 

With respect to the question whether water 
varies uniformly or otherwise in its capacity, 
I am inclined to think the increase, in this re- 
spect, will be found nearly proportional to the 
increase in bulk, and consequently will be four 
times as much at 212" as at the mean. Per- 
haps the expressions for the bulk may serve 
for the capacity ; if so, the ratios of the capa- 
cities at 32% 122* and 212* of the new scale, 
may be denoted by 22, 22| and 23. I should 
rather expect, however, that the ratios are 
much nearer equality, and that 200, 201 and 
204, would be nearer the truth.* 

* In the Lectures I delivered in Edinburgh and Glas- 
gow in the spring of 1807, I gave it as my opinion that 
the capacity of water at 32® was to that at 2I2«>, as 5 to 6, 
nearly. The opinion was founded on the fact I had just 
before observed, that a small mercurial thermometer at the 
temperature 31!'' being plunged into boilifjg water, rose to 
202O in 15"; but the same at 212° being plunged into 
jce-cold water, was 1 8" in descending to 42° ; estimating 
the capacities to be reciprocally as the times of cooling, it 
gave the ratio of 5 to 6. On more mature consideration I 
am persuaded this difference is occasioned, not so much by 
the difference of capacities, as by the different degrees of 
fluidity. Water of 212° is more fluid than water of 32°, 
and distributes the temperature with greater facility. By 
a subsequent experiment too, I find, that mercury cools a 


Dr. Crawford, when investigating the ac- 
curacy ot the common thermometer, was aware, 
that if equal portions of water of different 
temperatures were mixed together, and the 
thermometer always indicated the mean, this 
was not an infallible proof of its accuracy. 
He allows that if water have an increasing 
capacity, and the mercury expand increasingly 
with the temperature, an equation may be 
formed so as to deceive us. This is in fact 
the case in some degree ; and he appears to 
have been deceived by it. Yet the increased 
capacity of water, is by no means sufficient to 
balance the increased expansion of the mercu- 
ry, as appears from the following experiments. 

I took a vessel of tinned iron, the capacity 
of which was found to be equal to 2 oz. of 
water; into this were put 58 ourjces of water, 
making the sum = 60 ounces of water. The 
whole was raised to any proposed tempera- 
ture, and then two ounces of ice were put 
in and melted; the temperature was then ob- 
served, as follows : 

thermometer twice as fast as water, though it has but half 
its capacity for heat ; the times in which a thermometer is 
in cooling in fluids, are not, therefore, tests of their specific 


60 oz.water of 212° + 2 of 32% gave 200"f 
60 oz.water of 1 30°+ 2 of 32°, gave 1 22*' 
60 oz.water of 50°+ 2 of 32", gave 43".3 

From the first of these, 30 parts of water 
lost 1 1°^ each, or 345% and 1 part water of 
32° gained 168°l; the difference 345 — 168i 
= 176°|, expresses the number of degrees of 
temperature (such as are found between 200 
and 212 of the old scale) entering into ice of 
32° to convert it into water of 32°. Similar 
calculations being made for the other two, 
we find in the second, 150% and in the third, 
128°. These three resulting numbers are 
nearly as 5, 6 and 7. Hence it follows that 
as much heat is necessary to raise water 5° in 
the lower part of the old scale, as is required 
to raise it 7° in the higher, and 6° in the mid« 

Methods of finding the Specific Heats of 

The most obvious method of ascertaining the 
specific heats of bodies that have no chemical 

* Perhaps the above results may account for the diver- 
sity in authors respecting the quantity of latent heat (im- 
properly so called) in water. Respecting the doctrine of 
Black on Latent Heat, see an excellent note of Leslie. 
(Inquiry, page 529.) 


affinity for water, is to mix equal weights of 
water, and any proposed body of two known 
temperatures, and to mark, the temperature of 
the mixture. Thus, if a pound of water of 
32% and a pound of mercury of 212% be 
mixed, and brought to a common tempera- 
ture, the water will be raised vi degrees, and 
the mercury depressed ?i degrees; and their 
capacities or specific heats will be inversely 
as those numbers ; or, w I m '. '. specific heat of 
water '- specific heat of mercury. In this 
Way Black, Irvine, Crawford and Wilcke, 
approximated to the capacities of various bo- 
dies. Such bodies as have an affinity for water, 
may be confined in a vessel of known capa- 
city, and plunged into water so as to be heated 
or cooled, as in the former case. 

The results already obtained by this method 
are liable to two objections : 1st. the authors 
presume the capacities of bodies while they 
retain their form are permanent j that is, the 
specific heat increases exactly in proportion to 
the temperature; and 2d, that the common mer- 
curial thermometer is a true test of temperature. 
But it has been shewn that neither of these 
positions is warrantable. 

The calorimeter of Lavoisier and Laplace 
was an ingenious contrivance for the purpose of 
investigating specific heat ; it was calculated to 


shew the quantity of ice which any body heat- 
ed to a given temperature could melt. It was 
therefore not liable to the 2d objection above. 
Unfortunately this instrument does not seem to 
have answered well in practice. 

Meyer attempted to find the capacities of 
dried woods, by observing the times in which 
given equal volumes of them were in cooling. 
These times he considered as proportionate 
to the capacities bulk for bulk j and when 
the times were divided by the specific gravities, 
the quotient represented the capacities of equal 
weights. (Annal. de ChemieTom. 30). Leslie 
has since recommended a similar mode for 
liquids, and given us the results of his trials 
on 5 of them. From my own experience I 
am inclined to adopt this method as suscep- 
tible of great precision. The times in which 
bodies cool in like circumstances appear to 
be ascertainable this way with uncommon 
exactness, and as they are mostly very diiferent, 
a very small error is of little consequence. The 
results too I find to agree with those by mix- 
ture ; and they have the advantage of not 
being affected by any error in the thermome- 
tric scale. 

The formulae for exhibiting the phenomena 
of the specific heats of bodies are best con- 
ceived from the contemplation of cylindrical 


vessels of unequal bases. (See plate I. Fig. l). 
Supposing heat to be represented by a quantity 
of liquid in each vessel, and temperature by 
the height of the liquid in the vessel, the 
base denoting the zero or total privation of 
heat ; then the specific heats of bodies at any 
given temperature, Xy will be denoted by 
multipling the area of the several bases by 
the height or temperature, x. Those specific 
heats too will be directly as the bases, or as 
the increments of heat necessary to produce 
equal changes of temperature. 

Let w and W = the weights of two cold 
and hot bodies; c and C their capacities 
for heat at the same temperature (or the bases 
of the cylinders) ; d= the difference of the 
temperature of the two bodies before mixture, 
reckoned in degrees ; w = the elevation of the 
colder body, and ?i = the depression of the 
warmer after mixture, (supposing them to have 
no chemical action) ; then we obtain the fol- 
lowing equations. 

1. m + n = d. 

m = 

wc+W C 



4. c = 

w m 

l^ C —c, then, 5. m = — _- — 



If JV= Wy then, 6. C = "" "" 


To find the zero, or point of absolute pri- 
vation of temperature, from observations on 
the change of capacity in the same body. 
Let c = the less, and C = the greater capa- 
city, m = the number of degrees of the less 
capacity requisite to produce the change in 
equal weights, ft = the number of degrees 
of the greater capacity, x =. the whole num- 
ber of degrees of temperature down to zero ? 

7. Cx — cx = Cn = cm, 
_ C n c m 

To find the zero from mixing two bodies 
of the same temperature which act chemically, 
and produce a change of temperature. Let 
w, W, c, C &; X, be as before j \tt M = ca- 
pacity of the mixture, and n = the degrees of 


heat or cold produced : then the quantity of 
heat in both bodies will he ^ fc to + C W) x 
= (w + W) M X ± (w + W) M ji. 

(w + IV) M n 
9. and .r — 

(c w + C W) c/3 (IV + W) M 

It is to be regretted that so little improve- 
ment has been made for the last fifteen years in 
this department of science. Some of the earliest 
and most incorrect results are still obtruded 
upon the notice of students ; though with the 
least reflection their errors are obvious. I 
have made great number of experiments with 
a view to enlarge, but more especially, to 
correct the Tables of Specific Heat. It may 
be proper to relate some of the particulars. 
For liquids I used an egg-shaped thin glass 
vessel, capable of holding eight ounces of 
water; to this was adapted a cork, with a 
small circular hole, sufficient to admit the stem 
of a delicate thermometer tube, which had 
two small marks with a file, the one at 92% 
and the other at 82°, both being above the 
cork ; when the cork was in the neck of 
the bottle, the bulb of the thermometer was 
in the centre of the internal capacity. When 
an experiment was made the bottle was filled 
v/ith the proposed liquid, and heated a little 


above 92° ^ It was then suspended in the 

middle of a room, and the time accurately 

noted when the thermometer was at 92°, and 

again when it was 82°, another thermometer 

at the same time indicating the temperature 

of the air in the room. The capacity of the 

glass vessel was found = f oz. of water. 

The mean results of several experiments 

were as follow : 

Air in the Room 52°. 


Water cooled from 92'' to 82®, in 29 

Milk(1.026) 29 

Solution of carbonate of potash (1.30) 28| 

Solution of carbonate of ammonia (1.035) 28f 

Ammoniacal solution (.948) 28| 

Common vinegar (1.02) 27f 

Solution of common salt, 88 W. + 32 S. (1.197) 27 

SoluUon of soft sugar, 6 W. -f 4 S. (1.17) 26f 

Kitric acid (1.20) 26{ 

NLtrlcacid (1.30) 25$ 

Nitricacid (1.36) 25 

Sulphuric acid (1.844) and water, equal bulks fl. 535) 23| 

Muriaticacid (1.153) , 21 

Acetic acid (1.056) from Acet. Cop 2i 

Sulphuric acid (1.844) 19| 

Alcohol {.85) 19f 

Ditto (.817) I7i 

Ether sulphuric (.76) 15| 

Spermaceti oil (.87) 14 

These times would express accurately the 
specific heats of the several bodies> bulk for 
bulk, provided the heat of the glass vessel did 


not enter into consideration. But as the beat 
of that was proved to be equal to i of an 
ounce of water, or to -j of an ounce measure 
of oil, it is evident we must consider the 
heat disengaged in the 1st experiment, as from 

8 i ounces of water, and in the last as from 

9 i ounce measures of oil. On this account 
the numbers below 29 will require a small 
reduction, before they can be allowed to re- 
present the times of cooling of equal bulks of 
the different liquids; in the last experiment 
the reduction will be one minute, and less in 
all the preceding ones. 

It may be proper to observe, that the above 
results do not depend upon one trial of the 
several articles ; most of the experiments were 
repeated several times, and the times of cool- 
ing were found not to differ more than half a 
minute ; indeed, in general, there was no 
sensible differences. If the air in the room was, 
in any case, a little above or below 52% the due 
allowance was made. 

I found the specific heat of mercury, by 
mixture with water, and by the time of its cool- 
ing in a smaller vessel than the above, to be 
to that of water of equal bulk, as, .55 to 1 

I found the specific heats of the metals and 
other solids after the manner of Wiicke and 


Crawford ; having procured a goblet, of very 
thin glass and small stem, I found its capacity 
for heat; then put water into it, such that 
the water, together with the value of the glass 
in water, might be equal to the weight of 
the solid. The solid was raised to 212°, and 
suddenly plunged into the water, and the spe- 
cific heats of equal weights of the solid and 
the water, were inferred to be inversely as 
the changes of temperature which they expe- 
rienced, according to the 6th formula. Some 
regard was paid to the correction, on account 
of the error of the common thermometer, 
which was used on the occasion. The solids 
I tried were iron, copper, lead, tin, zinc, 
antimony, nickel, glass, pitcoal, &c. The 
results differed little from those of Wilcke and 
Crawford ; their numbers may, therefore, be 
adopted without any material error, till greater 
precision can be attained. In the following 
Table I have not carried the decimals bevond 
two places ; because present experience will 
not warrant further extension : the first place 
of decimals may, I believe, be relied upon as 
accurate, and the second generally so, but in 
a few instances it may, perhaps, be 1 or 2 
wrong ; except from this observation, the 
specific heats of the gases by Crawford, on 
which I shall further remark. 












SOLIDS. .^vts 






Dried woods, and other 

• 90? 



4 75* 


vegetable substances, 
from .45 to 


Common air 



Pit-coal (1 27) 



Carbonic acid 






Azotic - - 



Hydrat. lime 
Flint glass (2.87) 



Aqueous vapour - 



Muriate of soda 













1. 00 

1. 00 




Arterial blood 





Milk (1.026) 


1. 00 




Carbonat. of ammon. (1:035) 






Carboiiat. of potash ( 1 30) 



Antimony - 



Solut. of ammonia ( 948) 






Common vinegar (1 02) - 






Venous blood 




Solut. of common salt (1.197) 



Solut. of sugar (1.17) 



Oxides of the metal* sut 

Nitric acid (1.20) . 



pass the metals themselves, 

Nitric acid (i-3o) - 



accord ing to Crawford, 

Nitric acid (136) 



Nitrate of lime (r.40) 



Sulph acid and w^atcr, equal b 



Muriatic acid (1 153) 



Acetic acid fi.056) 



Sulphuric acid (1.844) 



Alcohol (.85) 



Ditto (-817) 



Sulphuric ether ( 76) 



Spermaceti oil (.S7) 







Remarks on the Table. 

The articles marked * arc from Crawford. 
Notwithstanding the ingenuity and address 
displayed in his experiments on the capacities 
of the elastic fluids, there is reason to believe 
his results are not very near approximations to 
the truth ; we can never expect accuracy v^hea 
it depends upon the observation of 1 or 2 
tenths of a degree of temperature after a tedi- 
ous and complicated process. Great merit is 
undoubtedly due to him for the attempt. — 
The difference between arterial and venous 
blood, on which he has founded the beauti- 
ful system of animal heat, is remarkable, 
and deserves further enquiry. 

From the observed capacities of water, so- 
lution of ammonia, and the combustibles, into 
which hydrogen enters, together with its small 
specific gravity, we cannot doubt but that this 
element possesses a very superior specific heat. 
Oxygen, and azote likewise, undoubtedly stand 
high, as water and ammonia indicate ; but the 
compound of these two elements denominated 
nitric acid, being so low, compared with the 
same joined to hydrogen, or water and ammo- 
nia, we must conclude that the superiority of 
the two last articles is chiefly due to the hydro- 
gen they contain. The elements, charcoal and 


sulphur, are remarkably low, and carry their 
character along with them into compounds, as 
oil, sulphuric acid, &c. 

Water appears to possess the greatest capa- 
city for heat of any pure liquid yet known, 
whether it be compared with equal bulks or 
weights ; indeed it may be doubted, whether 
any solid or liquid whatever contains more 
heat than an equal bulk of water of the same 
temperature. The great capacity of water 
arises from the strong affinity, which both its 
elements, hydrogen, and oxygen, have for 
heat. Hence it is that solutions of salts in 
water, contain generally less heat in a given 
volume than pure water: for, salts increase 
the volume of water as well as the density, 
and having mostly a small capacity for heat, 
they enlarge the volume of the water more 
than proportional to the heat they contribute. 

Pure ammonia seems to possess a high specific 
heat, judging from the aqueous solution, which 
contains only about 10 per cent. — If it could 
be exhibited pure in a liquid form, it would 
probably exceed water in this particular. 

The compounds of hydrogen and carbon, 
under the characters of oil, ether and alcohol, 
and the woods, all fall below the two last 
mentioned j the reason seems to be, because 
charcoal is an clement of a low specific heat. 


The acids form an interesting class of bedies 
in regwd to their specific heats. — Lavoisier is 
the only one who is nearly correcl in regard to 
nitiic acid ; he finds the specific heat of the 
acid 1.3 to be .66 j this with sonae other of his 
results I find rather too low. It is remaikable^ 
that the water in acid of this strength is 
63 per cent, and should have nearly as 
imich heat in it as the compound is found to 
have, whence it should seiem that the acid 
loses tiie principal part of its heat on cooibining 
with water. This is still more observable in 
muriatic acid, which contains 80 per cent, of 
water, and its specific heat is only .66 j whence 
not only the heat of the acid gas, but part of 
that in the water is expelled on the union ; this 
accounts for the great heat produced by the 
union of this acid gas with water. 

The specific heat of sulphuric acid has been 
well approximated by several. — Gadolin and 
Leslie make it .34, Lavoisier .33-)- ; Crawford 
finds it .43, but he must probably have had a 
diluted acid. 

CoHimon vinegar, being water whh 4 or 5 
per cent, of acid, does not differ materially 
from water in its specific heat; it has been 
stated at .39 and at .10; but such results do 
not require animadversion. The acetic acid 


I used contained 33 per cent, pure acidj 
this acid therefore, in combining with water, 
expo's much heat. 

Quicklime is determined by Lavoisier and 
Crawford to be .22 ; I think they have under- 
rated it : I find quicklime to impart as much 
or more heat than carbonate of lime, when 
inclosed in a vessel and plunged in water, or 
when mixed with oil. Hydrat of lime (that 
is, quicklime 3 parts and water 1 part, or dry 
slaked lime) is fixed at .28 bv Gadolin : it 
was .25 by my first experiments ; but I since 
find I have underrated it. The subject will be 
adverted to in a future section. 



Since the preceding section was printed off, 
I have spent some time in considering the 
constitution of elastic fluids with regard to 
heat. The results already obtained cannot be 
relied upon ; yet it is difficult to conceive and 
execute experiments less exceptionable than 
those of Crawford. It is extremely important. 


however, to obtain the exact specific heat of 
elastic fluids, because the phenomena of com- 
bustion and of heat in general, and conse- 
quently a great part of chemical agency, are 
intimately connected therewith. 

In speaking of the uncertainty of Crawford's 
results on the specific heat of elastic fluids, 
it must not be understood that all of them 
are equally implicated. The reiterated ex- 
periments on the heat giveti out by the com- 
bustion of hydrogen, in which it was found 
that 1 1 measures of mixed gases, when fired 
by electricity heated 20.5 measures of water 
2°. 4 (page 263) at a medium, were suscepti- 
ble of very considerable accuracy, and are 
therefore entitled to credit. The comparative 
heat of atmospheric air and water, which rested 
on the observance of nearrly 4 of a degree of 
temperature, is probably not very far from the 
truth ; but the very small differences in the 
heats communicated by equal bulks of oxygen, 
hydrogen, carbonic acid, azotic gas and com- 
mon air, together with the great importance 
of those differences in the calculation, render 
the results very uncertain. He justly observes^ 
that if we suppose the heats imparted by 
equal bulks of these gases to be equal, it will 
not aflfect his doctrine. The tenor of it neces- 
sarily led him to estimate the heat of oxygen 


high, compared with equal weights of carbo* 
nic acid and aqueous vapour, and of azotic 
gas or phlogisticated air, as it was then called, 
under the idea of its being an opjxjsite to oxy- 
gen or dephlogisticated air. Indeed his de- 
ductions respecting azotic gas, are not con- 
sistent with his expcrioients : for he makes no 
use of experiments 12 and 13, which are the 
only direct ones for the purpose, but he infers 
the beat of azotic gas from the observed differ- 
ence between oxygen and common air. The 
result gives it less than half that of common 
air ; whereas from the 1 3th experiment, scarcely 
any sensible difference was perceived between 
them. He has in all probability much under- 
rated it ; but his errors in this respect what- 
ever they may be, do not affect his system. 

When we consider that all elastic fluids are 
equally expanded by temperature, and that 
liquids and solids are not so, it should seem 
tha* a general law for the affection of elastic 
fluids for heat, ought to be more easily deduci- 
ble and more simp^le than one for liquids^ or 
solids. — There are three suppositions in regard 
to elastic fluids which merit discussion. 

1 . Equal iveights of elastic fluids may have 
the same quantity of heat under like circum- 
stances of temperature and pressure. 

The truth of this supposition is disproTed 


by several facts : oxygen and hydrogen upon 
their union give out much heat, though they 
form 8team» on elastic fluid of the same 
weight as the elements composing it. Nitrous 
gas aiui oxygen unite under similar circum- 
stances. Carbonic acid is formed by the unioa 
of charcoal, a substance of low specific heat^ 
with oxygen ; much heat is given out, which 
must be principally derived from the oxygen ; 
If then the charcoal contain little heat, and the 
oxygen combining with it be reduced, the 
carbonic acid must be far inferior in heat to an 
equal weight of oxygenous gas. 

2. Equal bulks of elastic fluids may hcpve 
the sdme quantity of heat with the same prep^ 
sure and temperature. 

This appears much more plausible ; the 
diminution of volume when a mixture of oxy- 
gen and hydrogen is converted into steam, may 
be occasioned by a proportionate diminution 
of the absolute heat j the same may be said of 
a mixture of nitrous gas and oxygen. The 
minute differences observed by Crawford, may 
have been inaccuracies occasioned by the com- 
plexity of his experiments. — But there are 
other considerations which render this suppo- 
sition extremely improbable, if they do not 
altogether disprove it. Carbonic acid contains 
it» own bulk of oxygen j the heat given outat 


its formation must therefore be exactly equal 
to the whole heat previously contained in the 
charcoal on tliis supposition ; but the heat by 
the combustion of one pound of charcoal 
seems, at least, equal to the heat by the com- 
bustion of a quantity of hydrogen sufficient to 
produce one pound of water, and this last is 
equal to, or more than the heat retained by 
the water, because steam is nearly twice the 
density of the elastic mixture from which it is 
produced ; it should therefore follow, that 
charcoal should be found of the same specific 
heat as water, whereas it is only about -^ of it* 
Were this supposition true, the specific heats of 
elastic fluids of equal weights would be in- 
versely as their specific gravities. — If that of 
steam or aqueous vapour were represented by 
1, oxygen would be .64, hydrogen 8.4, azote 
.72, and carbonic acid ,46. — But the supposi- 
tion is untenable. 

3. The quantity of heat belonging to the 
ultimate particles of all elastic fluids, must be 
the same under the same pressure and tem- 

It is evident the number of ultimate par- 
ticles or molecules in a given weight of volume 
of one gas is not the same as in another : for, 
if equal measures of azotic and oxygenous 
gases were mixed, and could be instantly 


united chemically, they would form nearly two 
measures of nitrous gas, having the same 
weight as the two original measures ; but the 
number of ultimate particles could at most be 
one half of that before the union. No two 
elastic fluids, probably, therefore, have the 
same number of particles, either in the same 
volume or the same weight. Suppose, then, 
a given volume of any elastic fluid to be con- 
stituted of particles, each surrounded with an 
atmosphere of heat repelling each other through 
the medium of those atmospheres, and in a 
state of equilibrium under the pressure of a 
constant force, such as the earth's atmosphere, 
also at the temperature of the surrounding 
bodies ; suppose further, that by some sudden 
change each malecule of air was endued with 
a stronger aflinity for heat ; query the change 
that would take place in consequence of this 
last supposition ? The only answer that can 
be given, as it appears to me, is this.— The 
particles will condense their respective atmos- 
pheres of heat, by which their mutual repul- 
sion will be diminished, and the external pres- 
sure will therefore eflfect a proportionate con- 
densation in the volume of air : neither an 
increase nor diminution in the quantity of heat 
around each malecule, or around the whole, 
will take place. Hence the truth of the sup^ 


position, or as it may now be called, proposi-. 
tion, is demonstrated. 

Corol. 1. The specific heats of equal weights 
of any two elastic fluids, are inversely as the 
weights of their atoms or molecules. 

2. The specific heats of equal 6?///r^ of elastic 
fluids, are directly as their specific gravities, 
and inversely as the weights of their atoms. 

3. Those elastic fluids that have their atoms 
the most condensed, have the strongest attrac- 
tion for heat j the greater attraction is spent 
in accumulating more heat in a given space or 
volume, but does not increase the quantity 
around any single atom;, 

4. When two elastic atoms unite by chemi- 
cal aflinrty to form one elastic atom, one half 
of their heat is disengaged. When three 
unite, then two thirds of their heat is disen^ 
gaged, &c- And in general, when m elastic 
particles by chemical union become n ; the 
heat given out is to the heat retained as m — n 
is to n. 

One objection to this proposition it may be 
proper to obviate : it will be said, an increase 
in the specific attraction of each atom must 
produce the same effect on the system as mi 
increase of external 'pressure. Now this last 
is known to express or give out a quantity of 
the absolute heat ; therefore the former must 


do the same. This conclusion must be admit- 
ted ; and it tends to establish the truth of the 
preceding proposition. The heat expressed by 
doubling the density of any elastic fluid amounts 
to about 50°, according to my former experi- 
ments J this heat is not so much as one hun- 
dreth part of the whole, as will be shewn 
hereafter, and therefore does not materially 
affect the specific heat : it seems to be merely 
the interstitial heat amongst the small globular 
molecules of air, and scarcely can be said to 
belong to them, because it is equally found in 
a vacuum or space devoid of air, as is proved 
by the increase of temperature upon admitting 
air into a vacuum. 

Before we can apply this doctrine to find the 
specific heat of elastic fluids, we must first 
ascertain the relative weights of their ultimate 
particles. Assuming at present what will be 
proved hereafter, that if the weight of an 
atom of hydrogen be 1, that of oxygen will be 
7, azote 5, nitrous gas 12, nitrous oxide 17, 
carbonic acid 19, ammoniacal gas 6, carbu- 
retted hydrogen 7, olefiant gas 6, nitric acid 
19, carbonic oxide 12, sulphuretted hydrogen 
16, muriatic acid 22, aqueous vapour 8, ethe^ 
real vapour 11, and alcoholic vapour 16; we 
shall have the specific heats of the several 
elastic fluids as in the following table. In 



order to compare them with that of water, 
we shall further assume the specific heat of 
water to that of steam as 6 to 7, or as 1 to 

Table of the specific heats of elastic fluids. 

Ilvdro^cn 9.382 

Azote 1.866 

Oxvaen 1.333 

Atmos.air 1.759 

Nitrous gas 777 

Nitrous oxide ... 549 
Carbonic acid... .491 
Animon. gas — 1.555 
Carb. hydrogen 1.333 

Olefiant gas 1.555 

Nitric acid 491 

Carbonic oxide .777 
Sulph. hydrogen .583 
Muriatic acid.. .424 
Aqueous vapour 1 .166 
Ether, vapour... .848 
Alcohol, vapour .586 
Water 1.000 

Let us now see how far these results will 
accord with experience. It is remarkable that 
the heat of common air comes out nearly the 
same as Crawford found it by experiment; 
also, hydrogen excels all the rest as he deter- 
mined ; but oxygen is much lower and azote 
higher. The principles of Crawford's doctrine 
of animal heat and combustion, however, are 
not at all affected with the change. Besides 
the reason already assigned for thinking that 
azote has been rated too low, we see from the 
Table, page 62, that ammonia, a compound 


of hydrogen and azote, has a higher specific 
heat than water, a similar compound of hydro- 
gen and oxygen. 

Upon the whole, there is not any established 
fact in regard to the specific heats of bodies, 
whether elastic or liquid, that is repugnant to 
the above table as far as I know ; and it is to 
be hoped, that some principle analogous to 
the one here adopted, may soon be extended 
to solid and liquid bodies in general. 




When certain bodies unite chemically wuth 
oxygen, the process is denominated combustion^ 
and is generally accompanied with the evolu- 
tion of heat, in consequence of the diminished 
capacities of the products. The fine attempt 
of Lavoisier and Laplace to find the quantities 
of heat disengaged during different species of 
combustion, has not been followed up with 
the attention ic deserves. Perhaps this may 
have been owing to the supposed necessity of 


using the calorimeter of the above philosophers, 
and to a notion that its results are not always 
to be depended upon. Much important in- 
formation may, however, be obtained on this 
subject by the use of a very simple apparatus, 
as will appear from what follows: 

I took a bladder, the bulk of which, whea 
extended with air, was equal to 3CXX)0 grains 
of water ; this was filled with any combustible 
gas, and a pipe and stop-cock adapted to it : 
a tinned vessel, capable of containing 30000 
grains of water was provided, and its capacity 
for heat being found, so much water was put 
into it as to make the vessel and water together, 
equal to 30000 grains of water. The gas was 
lighted, and the point of the small flame was 
applied to the concavity of the bottom of the 
tinned vessel, till the whole of the gas was 
consumed ; the increase of the temperature of 
the water was then carefully noted; whence the 
effect of the combustion of a given volume 
of gas, of the common pressure and tempera- 
ture, in raising the temperature of an equal 
volume of water, was ascertained, except a 
very small loss of heat by radiation, &c. which 
this method must be liable to, and which pro- 
bably does not exceed ^ or T^th of the whole. 

The mean results of several trials of the 
different gases are stated below -, when the 


experiments are performed with due care, 
there is scarcely any sensible differences in 
the results with the same species of gas. The 
point of the flame should just touch the bottom 
of the vessel. 

Hydrogen, combustion of it raises an 

equal volume of water 4°.5 

Coal gas, or carburetted hydrogen 10, — 

defiant gas 14. 

Carbonic oxide 4.5 

Oil, alcohol, and ether, were burned in a 
lamp, &c. and the effect observed as under : 

Oil, spermaceti, combustion of 10 grs. 

raised 30000 grs. water 5°. 

— of turpentine (much smoke unburnt) 3 

Alcohol (.8)7) 2.9 

Ether, sulphuric 3.1 

Tallow and wax.. 5.2 

Phosphor. — 1 Ogrs. heated SOOOOgrs. water 3 

Charcoal 2 

Sulphur 1 

Camphor 3.5 

Caoutchouc 2.1 

The five last articles were placed upon a 
convenient stand, and burned under the vessel 
of water ; except charcoal, a piece of which 


was ignited, then weighed, and the combus- 
tion was maintained by a gentle blast from a 
blow-pipe, directing the heat as much as pos- 
sible upon the bottom of the vessel ; after the 
operation it was again weighed, and the loss 
ascertained ; the result never amounted to 2" 
for ten grains, but generally approached it 

In order to exhibit the comparative effects 
more clearly, it may be proper to reduce the 
articles to a common weight, and to place 
along with them the quantity of oxygen known 
to combine with them. The quantity of heat 
given out may well be expressed by the num^ 
ber of pounds of ice which it would melt, 
taking it for granted that the quantity neces- 
sary to melt ice, is equal to that which would 
raise water 1 50° of the new scale. The re- 
sults may be seen in the following table. 

lib. hydrogen takes 7lbs. oxygen, prod, 8 Ibss water, melts 320lbs: ke. 

— carbur. hydrogen, 4 —— 5 wj & car. acid 85 ■■ ■ 

defiant gas, 3.5 4.5 88 

—— carbonic oxide, .«,8 — ^— 1.58 carb. acid 25 ■■ 

oil, wax and tal. 3.5 4.5 w. & car. ac. 104 ■ 

ether, 3 -— 4 — - 62 

posphorus 1.5 2.5 phoi. acid 60 ■ 

■ charcoal 2.8 — — 3,8 carb. acid 40 ■ 

■ sulphur — " ■ sulph. acid ao ■ 

— — camphor — — w. & car. ac; 70 —— 


Lavoisier has left us a similar table derived 
from experiments on the calorimeter, for hydro- 
gen, phosphorus, charcoal, oil and wax ; and 
Crawford for hydrogen, charcoal, oil and 
w^ax, derived from their combustion in ano- 
ther apparatus. By reducing Crawford^s re- 
sults to a comparative scale with Lavoisier's, 
they will both appear as follows : 

according to according to 
Lavosier. Crawford. 

lib Hydrogen by combustion melts 295lbs. ice 48olbs, ice. 

. — Phosphorus lOO — — — 

— Charcoal 96-5 — 69 — 

— Wax • 133. — 97 — 

_ Oil 148 — 89 — 

Hydrogen. The near coincidence of I^- 
vosier's result and mine is an argument in 
favour of their accuracy. Crawford, I think, 
must have overrated the heat produced ; his 
method of determining it, by the explosion of 
the gases by electricity, seems however sus- 
ceptible of precision, and ought to be repeat- 
ed. The truth perhaps lies between the two. 

Phosphorus. Lavoisier's result, which is 
much greater than mine, must, I think, be too 
high. I suspect that 66 is as much as can be 
fairly inferred. 

Charcoal. The inferiority of my results to 
those of Crawford is what might be expected. 


Mine must necessarily be rather too low. 
But Lavoisier is in this as well as all the 
other articles, hydrogen excepted, unwar- 
rantably too high. I think Crawford will 
be found too high j his experiments on the heat 
produced by the respiration of animals, sup- 
port this supposition. 

Wax and Oil. Crawford's results are a 
little lower than mine, which they ought not to 
be, and are doubtless below the truth. Lavoi- 
sier's certainly cannot be supported. This great 
philosopher was well aware of the uncertainty 
of his results, and expresses himself accord- 
ingly. He seems not to have had an adequate 
idea of the heat of hydrogen gas, which con- 
tributes so much to the quantity given out by 
its combustion ; he compares, and expects to 
find an equation, between the heat given out 
by burning wax, &c. and the heat given out 
by the combustion of equal weights of hydro- 
gen and charcoal in their separate state j but 
this cannot be expected, as both hydrogen and 
charcoal in a state of combination must contain 
less heat than when separate, agreeably to the 
general law of the evolution of heat on com- 
bination. — In fact, both Crawford and Lavoi- 
sier have been, in some degree, led away by 
the notion, that oxygenous gas was the sole 
or principal source of the light and heat pro- 


duced by combustion. This is the more re- 
markable of the former, after he had proved 
that hydrogenous gas, one of the most frequent 
and abundant combustibles, possessed nearly 
five times as much heat as the same weight of 
oxygenous gas. Azote, another combustible, 
possesses as high and probably higher specific 
heat than oxygen. Oil, wax, tallow, alcohol, 
&c. would be far from being low in the table 
of specific heat, provided a table were formed 
comprehending bodies of every class. Char- 
coal and sulphur rank but low in the table. 
Upon the whole then, we cannot adopt the 
language of Crawford, '^ that inflammable 
" bodies contain little absolute heat," and 
" that the heat which is produced by com- 
" bustion is derived from the air, and not from 
** the inflammable body." This language may 
be nearly right as applied to the ordinary com- 
bustion of charcoal and pitcoal ; but cannot 
be so when applied universally to combustible 

After these remarks it is almost unnecessary 
to add that the heat, and probably the light 
also, evolved by combustion, must be con- 
ceived to be derived both from the oxygen 
and the combustible body ; and that each 
contributes, for aught we know to the con- 


trary, in proportion to its specific heat before 
the combustion. A similar observation may 
be made upon the heat produced by the union 
of sulphur with the metals, and every other 
chemical union in which heat is evolved. 

Before wc conclude this section it may be 
proper to add, for the sake of those who are 
more immediately interested in the economy of 
fuel, that the heat given out by the com- 
bustion of lib. of charcoal, and perhaps also 
of pitcoal, is sufficient (if there were no loss) 
to raise 45 or 50 lbs. of water from the freeze- 
ing to the boiling temperature ; or it is suffici- 
ent to convert 7 or 8 lbs. of water into steam. 
If more than this weight of coal be used, there 
is a proportionate quantity of heat lost, which 
ought, if possible, to be avoided. 




Oi' absolute Privation of Heat. 

If we suppose a body at the ordinary tempe- 
rature to contain a given quantity of heat, like 
as a vessel contains a given quantity of water, 


it is plain that by abstracting successively small 
equal portions, the body v/ould finally be ex- 
hausted of the fluid. It is an object of pri- 
mary importance in the doctrine of heat to 
determine, how many degrees of the ordinary 
scale of temperature a body must be depres- 
sed before it would lose all its heat, or become 
absolutely cold. We have no means of effect- 
ing this by direct experiment ; but v/e can 
acquire data for a calculus, from which the 
zero may be approximated with considerable 

The data requisite for the calculus are the 
exact specific heats of the several bodies ope- 
rated upon, and the quantity of heat evolved, 
or absorbed by bodies, in cases of their che- 
mical combinations or otherwise. These data 
are not to be acquired without great care 
and circumspection; and hence the great 
diversity of the results hitherto obtained in 
this difficult investigation. According to some, 
the zero is estimated to be 900° below the 
common temperature ; whilst, according to 
others, it is nearly 8000° below the same. 
These are the extremes ; but various deter- 
minations of an intermediate nature are to be 

The most simple ca82 in theory is that of 


ice and water : supposing the capacities of 
these two bodies to be as 9 to 10, at the 
temperature of 32°, it is known that ice of 
32° requires as much heat as would raise water 
160°, to convert it into water of 32°, or to 
melt it. Consequently, according to the 8th 
formula, page 57, water of 32°, must contain 
10 times as much heat, or 1500°. That is, 
the zero must be placed at 1 500° below the 
temperature of freezing water. Unfortunately, 
however, the capacity of ice has not been 
determined with sufficient accuracy, partly 
because of its being a solid of a bad con- 
ducting power, but principally because the 
degrees of the common thermometer below 
freezing, are very erroneous from the equal 
division of the scale. 

Besides the one already mentioned, the 
principal subjects that have been used in this 
investigation are, 1st, mixtures of sulphuric 
acid and water; 2d, mixtures of lime and 
water ; 3d, mixture or combination of nitric 
acid and lime ; and 4th, combustion of hydro- 
gen, phosphorus and charcoal. Upon these 
it will be necessary to enlarge. 

Mixture of Sulphuric Acid and Water. 
According to the experiments of Lavoisier 


and Laplace on the calorimeter, a mixture of 
sulphuric acid and water in the proportion of 
4 to 3 by weight, determines the zero at 
7292° below freezing water, reckoning by 
Fahrenheit. But a mixture of 4 acid with 5 
water, determines the same at 2630°. 

Gadolin made several experiments on mix- 
tures of sulphuric acid and water, the results 
of which are as accurate as can be expected 
in a first essay of the kind. He has not de- 
termined the zero from his experiments, but 
taking it for granted to be 1400° below the 
freezing point on the supposition that the 
capacities of ice and water are as 9 to 10, he 
has enquired how far his experiments corro- 
borate the same, by comparing the capacities 
of the mixtures by experiment with those 
calculated from the previous assumption. His 
results are thus curtailed in their utility j but as 
he has given us data sufficient to calculate the 
zero from each experiment, it will be proper 
to see how far they accord with Lavoisier's, 
or those of others. 

Taking the specific heat of water at 1, Ga- 
dolin finds, by direct experiment, the specific 
heat bf concentrated sulphuric acid to be 
.339 (See Crawford on heat, page 465) ; he 
then mixes the acid and water in various 


proportions, observes the increase of temper- 
ature, and then finds the capacities of the 
mixtures. Whence we have data to find the 
zero by formula 9, page 58. In giving his 
numbers, I have changed his scale, the centi- 
grade, to Fahrenheit's. 



heat cvolv. 

capa. of mix. 

comp. zer 


+ 1 





+ 1 





+ 1 





+ 2 





+ 5 





+ 10 




The mean of these is 2300°, which is far 
beyond what Gadolin supposes to be the zero, 
as deduced from the relative capacities of 
ice and water, and to which he seeks to ac- 
commodate these experiments. 

As the heat evolved upon the mixture of 
sulphuric acid and water is so considerable, 
and as all three articles are liquids, and con- 
sequently admit of having their capacities as- 
certained with greater precision, I have long 
been occasionally pursuing the investigation 
of the zero from experiments on these liquids. 
The strongest sulphuric acid of 1.855, I find 
has the specific heat .33, and 


Acid Water sp. gr. heat evol. capa. of mix. zero 

5.77 4- 1 (1.78) 160° .420 6400o 

1.6 +1 (1.520) 260 .553 4150 

1 + 2 (1.230) 100 .764 6G0Q 

I reject all mixtures where the heat is less 
than 100°, because the difference between the 
observed capacity of the mixture, and the 
mean capacity is too small to be determined 
with precision. These results differ materially 
from Gadolin's. I believe they will be found 
to be nearer approximations to the truth. 
"When the two liquids are mixed in nearly 
equal weights, the results give the zero less 
remote than otherwise ; this appears to be the 
case both with Gadolin and me ; I have not 
yet been able to discover the cause of it ; per- 
haps the capacity of such mixture increases 
with the temperature more than in the other 

Lime and Wafer. 

Quicklime, that is, lime recently burned, has 
a strong affinity for watery when mixed in 
due proportion an intense heat is produced ; 
the lime falls, or becomes slaked, and then 
may be denominated hydrat of lime. IF no more 
water is put to quicklime than is sufficient to 
slake it, or pulverize it, three parts of lime, 


by weight, form four parts of hydrat, a per- 
fectly dry powder, from which the water 
cannot be expelled under a red heat. If more 
water is added, the mixture forms mortar, a 
pasty compound, from which the excess of 
water may be expelled by a boiling heat, and 
the hydrat remains a dry powder. When 
hydrat of lime and water are mixed, no heat 
is evolved ; hence the two form a mere mix- 
ture, and not a chemical compound. The 
heat then which is evolved in slaking lime, 
arises from the chemical union of three parts 
of lime and one of water, or from the forma- 
tion of the hydrat, and any excess of water 
diminishes the sensible heat produced. Before 
any use can be made of these facts for deter- 
mining the zero, it becomes necessary to de- 
termine the specific heat of dry hydrat of 
lime. For this purpose a given weight of 
lime is to be slaked with an excess of water ; 
the excess must then be expelled by heat till 
the hydrat is 4- heavier than the lime. A given 
weight of this powder may then be mixed 
with the same, or any other weight of water 
of another temperature, and its specific heat 
determined accordingly. By a variety of ex- 
periments made in this way, and with sundry 
variations, I find the specific heat of hydrat of 


lime about .40, and not .25 as in the table* 
page 62. Lime itself I find to be nearly .30. 
Crawford undervalues lime, by mixing cold 
lime with hot alcohol ; the lime does not pro- 
duce a sufficient effect on the alcohol, because 
it contains water, which acts upon the lime. 
I have no doubt a different specific heat would 
have been found, if cold alcohol had been 
poured on hot lime. The heat evolved in the 
formation of hydrat of lime may be found as 
follows : If 1 oz. of lime be put into 4 oz. of 
water, the temperature of the mixture will be 
raised 100"; in this case l^oz. hydrat is form- 
ed, and the heat evolved raises it together with 
3|- oz. water 100° ; but 3-^ water contains 7 
times the heat that 14- hydrat of lime does ; 
therefore the heat given out is sufficient to 
raise 8 times the hydrat 100", or once the hy- 
drat 800°. Whence the heat evolved by mixing 
3 parts of lime and 1 of water, is sufficient 
to raise the new compound 800°. Applying 
then the tlieorem in page 58, we obtain the 
zero = 4260° below the common temperature. 

Nitric Jcid and Lime. 

According to the experiments of Lavoisier 
and Laplace, the specific heat of nitric acid, 1.3, is .661, and that of lime .217, and a 
compound of 9y parts of said acid, and one 


of lime, is .619. Bat supposing there was 
no change of capacity upon combination, this 
compound should only have the capacity .618 ; 
whereas, in fact, the mixture produces an in- 
crease of temperature of about 180°, and 
therefore ought to be found with a diminished 
capacity, or one below .618. Were this fact 
to be established, it would exhibit an inex- 
plicable phenomenon, unless to those who 
adopt the notion oH free caloric and combined 
caloric existing in the same body, or to speak 
more properly, of caloric combined so as to 
retain all its characteristic properties, and car 
loric combined so as to lose the whole of them. 
Oae error in this statement has already been 
pointed out, in regard to the capacity of lime. 
If we adopt the specific heat of lime to be 
.30, and apply the theorem for the zero, W€ 
shall find it to be 15770° below the common 
temperature, as deduced from the above date 
io corrected. 

I took a specimen of nitric aeid of the spe- 
cific gravity 1.2, and found, by repeated trials, 
its specific heat to be .76 by weight. Into 
4600 grains of this acid of 35° temperature, 
in a thin flask, 657 grains of lime were gra- 
dually dropped, and the mixture moderately 
agitated ^ in one or two minutes after 3>4>ths of 
the lime was in and dissolved, the thermometer 


5-056 nearly to 212°, and the iTiixture was be- 
ginning to boil ; it was suffered to cool 20", 
when the rest oF the lime was added, and it 
again rose to the boiling point; about 15 
grains of insoluble residuum were left. These 
were taken out, and their place supplied by 
15 grains of fresh lime, which were dissolved^ 
and left a clear liquid nearly saturated, of 
1.334 sp. gravity. The specific heat of this was 
found to be .69. The increase of temperature 
being called 200°, and the specific heat of lime 
being .30, we find the zero to be 1 1000° be- 
low the freezing temperature. The experi- 
ment was» varied by taking acids of different 
strengths, and various proportions of lime, but 
the results still gave the zero more remote than 
either of the previous methods. Perhaps the 
reason may be that lime is still under-rated. 

Combustion of Hydrogen. 

Lavoisier finds the combustion of lib. of 
hydrogen to melt 295lbs. of ice. The results 
of my experience give 320lbs, and Crawford's 
480. — ^Till this fact can be more accurately 
ascertained, we may take 400ibs. as approxi- 
mating to the truth. Or, which amounts to 
the same thing, the combustion of Jib. of 
hydrogen takes 7lbs. of oxygen, and gives out 
heat which would raise 8lbs. of water 7500*„ 


By adopting Crawford's capacities of hydro- 
gen and oxygen, and applying the theorem, 
page 58, we find the zero 1290° from the 
common temperature. But If we adopt the 
preceding theory of the specific heat of elastic 
fluids, and apply the 4th corol. page 72, we 
must conclude that in the formation of steam, 
one half of the whole heat of both it^ ele* 
ments is given out ; the conversion of 81bs of 
steam into water, will give out heat sufficient 
to melt 56lbs. of ice; therefore one half of the 
whole heat in lib. of hydrogen, and 7lbs. of 
oxygen together, or which is the same thing, 
the whole heat in lib. of hydrogen, or Tibs, of 
oxygen separately, will melt 344lbs. of ice ; 
row if from 688 we take 400, there remain 
288 for the lbs. of ice, which the heat in 
8lbs. of water, at the ordinary temperature, is 
sufficient to melt, or the heat in lib. is capable 
of melting 36lbs. of ice : hence the zero will 
be 5400° below freezing water. 

Combustion of Phosphorus. 

One pound of phosphorus requires ^Ib. of 
oxygen, and melts 66lbs. of ice. The specific 
heat of phosphorus is not known ; but from 
analogy one may suppose it to have as much 
heat as oil, wax, tallow, &c. which is nearly 
half as much as water. From the last article 


it seems, that the whole heat in each lb. of oxy- 
gen is sufficient to melt 50lbs. of ice; whence 
the whole heat in both articles, previous to 
combustion, is sufficient to melt 75+18 
= 93lbs. of ice. From which deducting- 66, 
there remains 27 for the pounds of ice, which 
the heat in 2.5lbs. of phosphoric acid ought to 
melt. This would give the specific heat of 
that acid .30, a supposition not at all impro- 
bable. The result of the combustion of phos- 
phorus seems then to corroborate that from 

Combustion of Chaixoal. 

Crawford's data are, specific heat of char- 
coal .26, oxygen 4.749, carbonic acid 1.0454^ 
and the heat given out by burning lib. of 
charcoal = 69lbs. ice = 10350°. It is now 
established beyond doubt, that lib. of charcoal 
requires 2.6lbs. of oxygen to convert it into 
carbonic acid. From these data, by the theo- 
rem, page 58, we deduce the zero = 4400°. 

But Crawford himself has not noticed this 
deduction. If we adopt the theory of specific 
heat, and the table founded on it, combined 
with the supposition of the zero being 6000° 
below the common temperature, (see pag 74) 
v/e shall have from the general formula, thiwS 


(1+ 2.6) X .491 X // 
1 X .26 +2.6 x~i.'333~^ 3.6 ">r749i~ ^^^'' 

where h represents the degrees of temperature 
which the combustion of Jib. of charcoal 
would raise the product, or 3.6ibs. of car- 
bonic acid. From this, h is found = 6650'. 
But this heat would raise 3.6lbs. of water 
= 6650 X .491 = 3265°. Or it would raise 
lib. of water, 11750" ; or it would melt 78lbs. 
of ice. Lavoisier finds the effect = 961bs. 
and Crawford finds it = 69. So that the 
supposed distance of the zero is not discoun- 
tenanced by the combustion of charcoal, as 
far as the theory is concerned. 

Combustion of Oil, Wax and Talloic. 

We do not know the exact cotistitution of 
these compounds, nor the quantity of oxygen 
which they require ; but from the experiments 
of Lavoisier, as well as from some attempts 
of my own, I am inclined to think, that they 
are formed of about 5 parts of charcoal and I 
of hydrogen by weight, and that 6 parts re- 
quire 21 of oxygen for their combustion, form- 
ing 19 parts of carbonic acid and 8 of water. 
Let it be supposed that the zero is 6900° be- 
low freezing water, or that the heat in water 
of 32°, is sufficient to melt 46lbs. of ice, then 


the heat in steam will be sufficient to melt 
SSlfcs. By applying Cor. I, at page 72, we 
shall find the heat in oxygenous gas = 60.5lbs. 
affidd in carbonic aoid, 22.3lbs. The heat in 
lib. of m\y &c. equal to half that oi water 
= 28lbs. which being added to 211.7, the 
heat in 3.6lbs, of oxygen, gives 234.7lbs. of 
ice, whidh would be nwhed by all the heat 
in lib, of oil and 3.5 of oxygen ; but the pro- 
ducts of combustion ate l.Slb. of watser, and 
3.2lbs. of carbonic acid, together containing as 
mtjch heat as would melt 1 3 1 .2lbs. of ice ; this 
being subtracted from 23^4.7, leaves 103.5 for 
the ice to be melted by the boat evolved dum 
ing the combustioai of lib. of oil, wax or tal- 
low, which agrees with the experiment. The 
conclusion then supports the supposition, that 
the zero is 690(y below freezir^ wfiter. 

Combustion of EihePy 8Cc. 

I have pretty accurately ascertained the pro- 
ducts of the combustion of lib. of ether to be 
1.75 water, and 2.25 carbonic acid, derived 
from its union with Slbs. of oxygen. By m- 
stituting a calculation similar to the above, 
but on the supposition of the zero being 6000' 
below freezing water, I find the heat given 
out on the combustion of ether, ought to be 
= 67lbs. of ice : it was observed to be 62, and 


the difference may well be attributed to the 
loss unavoidable in my method of observa- 

I might here enquire into the results of the 
combustion of the other articles mentioned in 
the table, page 78, as far as they affect the 
present question s, but I consider those above 
noticed as the most to be depended upon. 
From the result of olefiant gas we may learn, 
that a combustible body in the gaseous state, 
does not give out much more heat than when 
in a liquid state ; for, oil and olefiant gas cer- 
tainly do not differ much in their constitution ; 
one would therefore have expected the same 
weight of olefiant gas to have yielded more 
heat than oil, because of the heat required to 
maintain the elastic state ; but it should seem 
that the heat requisite to convert a liquid to 
an elastic fluid, is but a small portion of the 
whole, a conclusion evidently countenanced 
by the experiments and observations contained 
in the preceding pages. 

It may be proper now to draw up the re- 
sults of my experience, reported in the present 
section, into one point of view. 


Zero below 



From a mixture of 5.77 sulphuric acid and 1 water 6400^ 

1.6 1 4130 

1 2 6000 

3 lime 1 4^60 

7 nitric acid 1 lime 11000 

iTom the combustion of hydrogen 5400 

phosphorus 5400 

charcoal 6000 

. oil, wax and tallow 6900 

ether 6000 

The mean of all these is 6150°. We are 
authorised then, till something more decisive 
appear, to consider the natural zero of tem- 
perature as being about 6000° below the tem- 
perature of freezing water, according to the 
divisions of Fahrenheit's scale. The differences 
of the above results are not greater than what 
may be ascribed to inaccuracies, except the 
2d and 5th. I believe it will be impossible 
to reconcile these two to each other, unless 
it is upon the supposition of a change of capa- 
city with change of temperature in one or 
both of the mixtures. This deserves farther 

Heat produced by Percussion and Frictio n 

The heat produced by the percussion and 
friction of solid bodies, arises from one and 


the same cause, namely, from a condensation 
of volume, and consequent diminution of 
capacity of the excited body ; exactly in the 
same manner as the condensation of air pro- 
duces heat. It is a well known fact, that iron 
and other metals, by being hammered, be« 
come hot and condensed in volume at the 
same time; and if a diminution of capacity 
has not been observed it is because it is small, 
and has not been investigated with sufficient 
accuracy. That a change of capacity actually 
takes place cannot be doubted, when it is 
considered, that a piece of iron once hammered 
in this way, is unfitted for a repetition of the 
effect, tin it has been heated in a fire and 
cooled gradually. Count Rumford has fur- 
nished us with some important facts on the 
production of heat by friction. He found that 
in boring a cannon for 30 minutes, the tempe- 
rature was raised 70° ; and that it suffered a 
loss of 837 grains by the dust, and scales torn 
ofT, which amounted to -^-gr part of the cylin^ 
der. On the supposition that all the heat was 
given out by these scales, he finds they must 
have lost 66360° of temperature j when at the 
same time he found their specific heat not sen- 
sibly diminished. But this is manifestly an 
incorrect view of the subject : the heat ex.cited 
does not arise from the scales merely, else how 


should hammering make a body red hot with- 
out any loss of scales ? The fact is, the whole 
mass of metal is more or less condensed by 
the violence used in boring, and a rise of 
temperature of 70 or 100° is too small to pro- 
duce a sensible diminution in its capacity for 
heat. Does Count Rumiford suppose, that if 
in this case the quantity of metal operated 
upon had been lib. and the dust produced 
the same as above, that the whole quantity of 
heat evolved would have been the same ? 

The phenomena of heat produced by fric- 
tion and percussion, however, sufficiently shew 
that the zero of temperature cannot be placed 
at so small a distance as 1000° or 1500" below 
the common temperature, as has been deter- 
mined by some philosophers. 




Arising from inequaliti) of Temperature. 

As from various sources the temperature of 
bodies is liable to perpetual fluctuation, I't 
becomes of importance to determine the nature 


of the motion of heat in the same body, and 
in its passage from one body to another, aris- 
ing from its incessant tendency to an equili- 

A solid bar being heated at one end, and 
exposed to the air, the heat is partly dissipated 
in the air, and partly conducted along the bar, 
exhibiting a gradation of temperature from 
the hot to the cold end. This power of 
conducting heat varies greatly, according to 
the nature of the subject : in general, metals, 
and those bodies which are good conductors 
of electricity, are likewise good conductors of 
heat ; and vice versa. 

When a fluid is heated at its surface, the 
heat gradually and slowly descends in the 
same manner as along a solid 3 and fluids seem 
to have a difference in their conducting power 
analogous to that of solids. But when the 
heat is applied to the bottom of a vessel, 
containing a fluid, the case is very different ; 
the heated particles of the fluid, in conse- 
quence of their diminished specific gravity, 
form an ascending current and rise to the sur- 
face, communicating a portion of heat in their 
ascent to the contiguous particles, but still 
retaining a superiority of temperature ; so that 
the increase of temperature in the mass is first 
observed at the surface, and is constantly 


greatest there till the commencement of ebul- 
lition in liquids, at which period the tempera- 
ture is uniform. The conducting power of 
fluids then arises from two distinct sources ; the 
one is the same as in solids, namely, a gradual 
progress of the heat from particle to particle, 
exclusive of any motion of the particles them- 
selves ; the other arises from the internal mo- 
tion of the particles of the fluid, by which the 
extremes of hot and cold are perpetually 
brought into contact, and the heat is thus dif- 
fused with great celerity. The latter source 
is so much more effectual than the former, 
that som.e have been led, though without 
sufficient reason, to doubt the existence of 
the former, or that fluids do convey heat in the 
same manner as solids. 

Nothing appears, then, but that the com- 
munication of heat from particle to particle, is 
performed in the same way in fluids as in solids; 
the rapidity of its diffusion in fluids, is to be 
ascribed to an hydrostatical law. But there 
is another method by which heat is propagated 
through a vacuum, and through elastic fluids, 
which demands our particular notice. By 
this we receive the heat of the sun ; and by 
this, when in a room, we receive the heat of 
an ordinary fire. It is called the radiation of 


heat ; and the heat, so propelled, is called ra^ 
diant heat. 

Till lately we have been used to consider 
the light and heat of the sun as the same 
thing. But Dr. Herschel has shewn, that there 
are rays of heat proceeding from the sun, 
which are separable by a prism from the rays 
of light j they are subject to reflection, like 
light J and to refraction, but in a less degree, 
which is the cause of their separability from 
light. The velocity of radiant heat is not 
known J but it maybe presumed to be the 
same as that of light, till something appears 
to the contrary. An ordinary fire, red hot 
charcoal, or indeed any heated body, radiates 
heat, which is capable of being reflected to a 
focus, like the light and heat of the sun ; but 
it should seem to be not of sufficient energy 
to penetrate glass, or other transparent bodies 
so as to be refracted to an efficient focus. 

Several new and important facts relative to 
the radiation of heat, have lately been ascer- 
tained by Professor Leslie, and published in 
his " Enquiry on Heat." Having invented 
an ingenious and delicate air thermometer, 
well adapted for the purpose, he was enabled 
to ma k the effects of radiation in a great 
variety of cases and circumstances, with more 
precision than had previously been done. Some 


of the principal facts respecting the radlati<$r> 
of heat, which have either been discovered or 
con6rmed by him, it will be proper to mtVr 

1. If a given vessel be filled with hot water, 
the quantity of heat which radiates from it, 
depends chiefly upon the nature of the ex-» 
tenor surface of the vessel. Thuv if a canis- 
ter of tinned iron be the vessel, then a certain 
quantity of heat radiates from it; if the said 
vessel be covered with black paint, paper, 
glass, &c, it will then radiate 8 times as much 
heat in like circumstances. 

2. If the bulb of the thermometer be cover- 
ed with tinfoil, the impression of the radiant 
heat is only |th of that upon the glass sur- 

3. A metallic mirror reflects IG times aj 
much heat from an ordinary fire, or from any 
heated body, as a similar glass mirror does. 
This last is found to reflect the heat from its 
anterior surface, and not from the quicksilver- 
ed one, which is the most essential in refkcting 
solar light and heat. Here then is a strik- 
ing difference between solar and culinary 

From these facts it appears, tliat mets^ 
and other bodies which are eminently dispos- 
ed to rcjiect radiant heat, are not disposed to 


absorb it in any remarkable degree ; whereas, 
black paint, paper, glass, &c. are disposed to 
absorb it, and consequently to radiate it again 
in proper circumstances. 

4. Screens of glass, paper, tinfoil, &c. being 
placed between the radiating body and the 
reflector, were proved to intercept the radiant 
heat completely ; but being heated themselves 
by the direct radiant heat, in time the ther- 
mometer was affected by their radiation. — ■ 
The heat radiating from hot water, does not 
then seem capable of being transmitted through 
glass, like the solar heat. 

5. Radiant heat suffers no sensible loss in its 
passage through the air ; a greater or less 
radiant body produces the same effect, pro- 
vided it subtends the same angle at the re- 
flector, agreeing with light in this respect. 

6. The intensity of reflected heat diminishes 
inversely as the distance ; whereas, in light, 
it is the same at all distances; the focus of 
heat too differs from that of light ; it is nearer 
the reflector ; the heating effect diminishes 
rapidly in going outwards, but slowly in go- 
ing inwards towards the reflector. — This seems 
to intimate the want of perfect elasticity in 
radiant heat. 

7. A hollow globe of tin, four inches in 
diameter, being filled with hot water, cooled 


from 35° to 25° centigrade in 156 minutes; the 
same painted with lamp-black, cooled from 
35° to 25° in 81 minutes. The air of the room 
was 15°. 

8. When a heated body is whirled through 
the air, the additional cooling effect is directly 
proportional to the velocity. 

9. In air the rate of cooling of a hollow- 
glass globe filled with hot water, and that of 
the same globe covered with tinfoil, is not con- 
stant at all temperatures. The disproportion 
is greater in low temperatures, and less in 
high. Thus, in the present case, Mr. Leslie 
finds the variable ratio to be as 105 -i- h for 
glass, and as 50 + h for tin, where 1l repre- 
sents the elevation of temperature in degrees. 
According to this the rate of cooling of a 
vitreous and a metallic surface is nearly the 
same at very high temperatures ; but is nearly 
as 105 to 50, when h is very little. — No dif- 
ferences are observed in their rates of cooling 
in water. 

10. After a long and intricate, but ingenious 
investigation, Mr. Leslie finds the cooling 
power of the air upon a hollow sphere, six 
inches in diameter, and filled with boiling 
water, to be as follows : namely, in each 
minute of time the fluid loses the following 


fractional parts of its excess of temperature, 
hy the three distinct sources of refrigeration in 
the air undermentioned : 

By abduction, that is, the proper conduct- 
ing power of air, the 524th. 

By recession, that is, the perpendicular cur- 
rent of air excited by the heated body, the 
h X 21715th. 

By pulsation, or radiation, the 2533d part 
from a metahc surface, and eight times as 
much, or the 317th part from a surface of 
paper j (It should be observed, that Mr. Les- 
lie contends that air is instrumental in the ra- 
diation of heat, which is contrary to the re- 
ceived opinion.) 

11 . A body cools more slowly in rarefied 
air, than in air of the common density : and 
the different species of air have their respective 
refrigerating powers. Common air and hydro- 
genous gas exhibit remarkable difJerences. Ac- 
cording to Mr. Leslie, if the cooling power 
of common air upon a vitreous surface be de- 
noted by unity, that of hydrogenous gas will 
be denoted by 2,2857 ; and upon a metallic 
surface the ratio is .5 to 1.7857. In common 
air the loss from a vitreous surface is .57 by ra- 
diation, and .43 by the other two causes : from 
a metallic surface, .07 and .43. In hydroge- 
nous gas the loss from a vitreous surface is .57 


by radiation, and 1.71 by the other causes j 
from a metallic surface, .07 and 1 .7 1 . — He finds 
the radiation to be the same in the two 'gases, 
and to be very little diminished by rarefac- 
tion ; but the effects of the other refrigerating 
powers rapidly diminish with the density. 

Those who wish to see the experiments 
and reasonings from which these important 
conclusions are derived, must have recourse to 
Mr. Leslie's work : but as some of the facts 
and opinions appear from my experience to be 
questionable, I shall now proceed to state 
what has occurred to me on these subjects. — 
I have no reason to withhold my assent from 
the first 8 articles j but the last 3 are not 
equally satisfactory. 

Before we enter upon a detail of experi- 
ments, it will be proper to point out the cor- 
respondence of the new thermometric scale 
with the old one in the higher parts, it being 
only given briefly in the table, page 14. 



Correspondences of the Tkermometric Scales. 

old scale. 

new scale. 

old scale. 

new scale. 


212° I 

409°. 8 



002 ' 

427. 3 




445. 3 




463. 6 




482. 2 












539. 7 




559. 8 




580. I 




600. 7 










Experiment 1 . 

A mercurial thermometer having a bulb of 
half an in inch in diameter, and a scale of 
about 8 inches long from freezing to boiling 
mercury, was heated to 442° new scale, and 
suffered to cool in a horizontal position in air 
of 42^ The bulb in this and every other in- 
strument projected several inches below the 
scale. The times of cooling were the same 
from 442° to 242°, from 242° to 142°, and from 
142° to 92°, namely, 2 minutes and 20 seconds 
each. This was often repeated i the times of 
cooling were always within 4 or 5 seconds of 
that above, and when any differences in the 


successive intervals took place, the times were 
always observed to be rather less in the higher, 
and more in the lower parts of the scale. 

From this experiment it appears, that the 
thermometer was raised 400° above the tem- 
perature of the air, or to 600° of the old scale ; 
it lost 200° of temperature in the first interval 
of time, 100' in the second, and 50° in the 
third. This' result goes to establish the prin- 
ciple announced at page 12, that, according 
to the new graduation, the temperature descends 
in geometrical progression to equal increments 
of time. 

Experiment 2. 

According to Mr. Leslie, the same law of 
cooling does not take place from a metallic 
as from a vitreous surface ; this always ap- 
peared to me very surprising, and I was 
anxious to satisfy myself more particularly as 
to the fact. AVith this view, I took another 
mercurial thermometer, with a bulb of .7 inch 
diameter, and scale of 12 inches, having a 
range from to 300° old scale, and corres- 
ponding new scale attached to it. This was 
heated, and the times of cooling through every 
successive 10 degrees of the new scale v/ere 
noticed repeatedly ; the bulb was then covered 


with tinfoil, pasted upon it, and the surface 
made as smoolh as well could be ; the ther- 
mometer was then heated, and the times of 
cooling were again noticed as betore, re- 
peatedly. The mean results follow ; and a 
column of the differences of the logarithms of 
the degrees expressing the elevation of tem- 
perature above that of the surrounding air, 
which was 40°. The temperature of the 
thermometer was raised to 275° per scale ; that 
is, 235° above the air, and it is obviously most 
convenient to reckon from the temperature of 
the air considered as zero : in which case 19 
represents the difference of the logarithms of 
235 and 225, &c. 

Bulb clf »r. 

Bulb cov. 

Dif. of 

Thermom. cooled. 


with tinfuiL 


Tram 835P 


2259 in 11 





































































































































By inspecting this table, it appears that the 
whole time of cooling when the bnlb was 
clear was 8 51 seconds, and when covered! 
with tinfoil was 1206 seconds, which numbers 
are nearly as 17 to 24. But the times in 
cooling from 175° to 155'* were 17 and 24 se- 
conds respectively ; and the times in cooling 
from 95° to 85° were 34 and 48 respec- 
tively, which are exactly in the ratio of the 
whole times: and by examining any two cor* 
responding times, they will be found to be as 
17 to 24 nearly. Whence it follows that t!«e 
same law of progressive cooling applfes to a 
metallic as to a vitreous surface, contrary to 
the results of Mr. Leslie's experience. It 
must not however be understood that this 
ratio for the two kinds of surfaces is quite 
correct ; however carefully the bulb of a ther- 
mometer may be coated with tinfoil, the sur- 
face is necessarily enlarged, which makes it 
cool more quickly than if the metallic Surface 
were the very same qviantity as the vitreous. 

The differences of the logarithms happening 
accidentally so nearly to coincide in magttrttnde 
with the tim« of cooling of tht metallic sur- 
face, tlrcy rcqiitre no reduction, and we have 
an opportunity of seeing how f^ar the law of 
geometrital progression In cooling is supported 
by this experhncnf . It appears that for 5 or 6 


of the highest intervals of temperature, the 
times of cooling were rather smaller, and for 
the two last rather larger than required by 
the law. 

Experiment 3. 

As Mr. Leslie found the times of cooling: 
of metallic surfaces considerably enlarged, in 
moderate elevations of temperature more es- 
pecially, I took another thermometer having 
a smaller bulb, and a scale of an inch for 10 
degrees, this was treated as in the last experii 
ment, and the results were asunder : 

Thermom. cooled. 


lib clear. 

Bulli coated 

Lo^. ratios 


with tinfoil. 



rrom r.?^' 











































729 874 875 

Here the whole times of cooling, and the 
several parts are almost accurately as 10 for 
the vitreous, and as 12 for the metallic surface. 
They very nearly accord too with the logarith- 
mic ratios. The effect of the metallic sur- 
face diflfers less from that of the vitreous in 


this than in the former experiment ; because 
the bulb being smaller, it was more than pro- 
portionally increased in surface by the tinfoil, 
which was pasted on in small slips, and conse- 
quently was twofold in many places. 

Being from these results pretty well satisfied 
that the surfaces of bodies do not disturb the 
law of their refrigeration, though they ma- 
terially affect the time, yet in consequence of 
the general accuracy of Mr. Leslie's experi- 
ments, I was desirous to ascertain the results in 
his own way, more particularly because for the 
reason assigned above, my method did not give 
the true rates of cooling of equal surfaces. 

Experiment 4. 

I took two new tin canisters, such as are 
commonly used for tea, of a cylindrico-conical 
shape, and each capable of holding 15 oz. of 
water. The surface of one of them v>/as co- 
vered with brown paper pasted on it ; instead 
of the usual lid, a cork of 1^ inch, diameter 
was adapted to both, and through a hole in 
the centre of this, the tube of a delicate ther- 
mometer was inserted, with a scale of the new 
graduation affixed above the cork. Both 
canisters were contrived to be suspended by 
small strings when filled with water, and lo 


have the thermometer with its bulb in their 
centers. They were successively filled with 
boiling water, and suspended in the middle of 
a room of the temperature 40°, and the times of 
cooling through each successive 10 degrees 
were noticed as below. 

Water cooled. 

Canister covered 




th paper. 








6.5 ta\n. 

10 min. 












11 + 




































































219 327.5 330 

Here the results are equally satisfactory and 
important ; not only the times of cooling are 
in the uniform ratio of 2 to 3 throughout the 
range ; but they almost exactly accord with 
the logarithmic ratios, indicating the geometric 
progression in cooling. As experiments of 
this sort are capable of being repeated by any 
one without the aid of any expensive instru- 
ment or any extraordinary dexterity ; it will 


be unnecessary to insist upon the accuracy of 
the above, ft will be understood that the 
range of cooling was from 205° of the new 
scale, to 65° of the same, the air being 40% or 
25° below the extremity of the range, which 
corresponds with 57° of the old scale. 

It will be proper now to enquire into thd 
cause of the difference in the times of cooling 
arising from the variation of surface. Mr. 
Leslie has shewn the surface has no influence 
upon the time of cooling when immersed in 
water ; it should seem then that the difference 
of surfaces in the expenditure of heat arises 
from their different powers of radiation solely; 
indeed Leslie has proved by direct experiments 
that the heat radiating from a vitreous or pa- 
per surface is 8 times as great as that from a 
metallic surface. Taking this for granted, we 
can easily find the portions of heat dispersed by 
radiation, and conducted away by the atmos- 
phere. For, let 1 denote the quantity of heat 
conducted away by the atmosphere, from a 
vitreous or metallic surface in any given small 
portion of time, and x the quantity radiated 
from a metallic surface in the same time ; then 
8j will be the quantity radiated from a vitreous 
surface in that time ; and from the result of 
the last experiment we shall have, 2 : 3 :: 1+x : 
1 + Srs whence 2 4- 16jr = 3 4- 3j:, and 


x =z j-^ J this gives 1 ,-^3, for the whole heat 
discharged by metal, and 1 f-^ for that dis- 
charged by glass in the same time, where the 
unit expresses the part conducted, and the 
fraction the part radiated. 

That is, from a metallic surface 13 parts of 
heat are conducted away by the air and 1 part 
radiated j from a vitreous surface 13 parts 
are conducted, and 8 parts radiated, in a given 

The quantity of heat discharged by radia- 
tion from the most favourable surface, there- 
fore, is probably not more than .4 of the whole, 
and that conducted away by the air not less 
than .6. — Mr. Leslie however deduces ,57 for 
the former, and .43 for the latter j because he 
found the disproportion in the times of cooling 
of vitreous and metallic surfaces greater than 
I find it in the lov/er part of the scale. 

The obvious consequences of this doctrine 
in a practical sense are, 

1. In every case where heat is required to 
be retained as long as possible, the containing 
vessel should be of metal, with a bright clear 

2. Whenever heat is required to be given 
out by a body with as much celerity as pos- 
sible, the containing vessel, if of metal, ought 
to be painted, covered with paper, char- 


coal, or some animal or vegetable matter ; in 
which case the heat given out will be 3 parts 
for 2 from a metallic surface. 

Refrigeration of Bodies in 'various Kinds of 
Elastic Fluids. 

Bodies cool in very different times in some 
of the clastic nuids. Mr. Leslie was the first, 
I believe, who noticed this fact ; and he has 
given us the results of his experiments on com- 
mon air and hydrogenous gas, of the common 
density, and also rarefied in various degrees. — 
I made some experiments with a view to de- 
termine the relative cooling powers of the 
gases, the results of which it may be proper to 
give. My apparatus was a strong phial, con- 
taining about \o or 20 cubic inches ; a per- 
forated cork containing the stem of a ther- 
mometer was adapted to it, so as to be air 
tight j two marks were made with a file on 
the tube of the thermometer, comprizing an 
interval of 15 or 20°, about blood heat. The 
bottle was filled with any proposed gas, and 
after it had acquired the temperature of the 
surrounding air, the stopper was withdrawn, 
and the heated thermometer with its cork was 
instantiv inserted ; the number of seconds 


which elapsed whilst the mercury descended 
from the upper to the under mark were then 
noted, as under. The surrounding air was of a 
constant temperature. 

Thermometer immersed f cooled in 

In carbonic acid gas j 1 12 seconds. 

— sulphuretted hydrogen, ni-"\ 

trous oxide, and defiant > 100 + 

gas 3 

— com. air, azotic and oxyg. gas 100 

— nitrous gas 90 

— carburet, hyd. or coal gas .... 70 

— hydrogen 40 

The refrigerating effect of hydrogen is truly 
remarkable; I cooled the thermometer 10 
times successively in a bottle of hydrogen gas ; 
at each experiment the instrument was taken 
out, and the stopper put in, till the original 
temperature was restored ; by this, a portion 
of the hydrogen escaped each time, and an 
equal portion of common air was admitted ; 
the times of cooling regularly increased as 
follows; viz. 40, 43, 46, 48, 51,53, 56, 58, 
60 and 62 seconds, respectively ; at this time 
the mixture was examined, and found half 
hydrogen and half common air. Equal 
measures of hydrogen and common air were 


then mixed together, and put into the bot- 
tle, and the heated thermometer was found 
to cool from mark to mark, in 62 seconds as 

Condensed air cools bodies more rapidly 
than air of common density ; and rarefied air 
less rapidly, whatever be the kind. — The re- 
sults of my own experience for common air 
were as follows : 

Density o&the air. Therm, cools in 

2 85 seconds, 

1 100 

t 116 

^ 128 

T 140 

tV 16a 

,\ 170 

A small receiver of hydrogen gas, which 
cooled the thermometer in 40 seconds, when 
rarefied 7 or 8 times, took 70 seconds to cool 
the same. But the exact effects of rarefaction 
on this and the other gases were not deter- 

From Mr. Leslie, we learn that in hydro- 
genous gas, there is little difference between 
the time of cooling of a vitreous and metallic 
surface, the former being as 2.28, and the lat- 


ter as 1.78, from which he justly infers *' this 
inequality of effect [between atmospheric air 
and hydrogenous gas] proves its influence to 
be exerted chiefly, if not entirely, in augment- 
ing the abductive portion." 

The expenditure of heat by radiation being 
the same in hydrogenous gas as in atmospheric 
air, we may infer it is the same in every other 
species of gas ; and therefore is performed in- 
dependently of the gas, and is carried on the 
same in vacuo as in air. Indeed Mr. Leslie 
himself admits that the diminution of the 
effect consequent upon rarefaction is extremely 
small, which can scarcely be conceived if air 
were the medium of radiation. 

The effect of radiation being allowed con- 
stant, that of the density of the air may be 
investigated, and will be found, I believe, to 
vary nearly or accurately as the cube root of the 
density. In order to compare this hypothesis 
with observation, let 100 = time of cooling in 
atmospheric air, the density being 1 ; then 
from what has been said above,. 4 will represent 
the heat lost by a vitreous surface by radiation, 
and .6 that lost by the conducting power of 
the medium. Let t = the time of cooling in 
air of the density d ; then if 100 : .4 v. t -. .004 
t = the heat lost by radiation ; but the heat 
conducted away is, by hypothesis, as the time 


X by the cube root of the density = .006 

3 a 

W d; whence .004^+ .006 ty/d= 1, and 



.004 + .006v/rf 

Calculating from this formula, we shall find 
the times of cooling in common air of the 
several densities as under : 

Den»ity of the air. Times of cooling. 

2 86.5 seconds. 

1 100 

t 114 

^ 129 

4 143 

-^ 157 

^ 170 

TT 182 

tU 193 

_-i_ 250 


This table accords nearly with the preceding 
one, the result of actual observation. — In the 
same way might the times of cooling of a me- 
tallic surface in rarefied air be found, by sub- 
stituting .0007 for .004, and .0093 for .006 in 
the preceding formula. 

The cooling power of hydrogenous gas in- 
dependent of radiation, may be found thus : 


if 100" : .4 :: 40" : .16 = the heat lost by 
radiation in that gas in 40 seconds ; whence 
,84 = the heat conducted away by the air in 
40", or .021 per second ; but in common air 
the loss per second by abduction is only .006 ; 
from this it appears that the refrigerating 
power of hydrogenous gas is 3t tiroes as great 
as that of common air. 

It may be asked what is the cause why dif- 
ferent gases have such different cooling effects, 
especially on the supposition of each atom of 
all the different species possessing the same 
quantity of heat ? To this we may answer 
that the gases differ from each other in two 
essential points, in the number of atoms in a 
given volume, and in the weight or inertia of 
their respective atoms. Now both number and 
weight tend to retard the motion of a current : 
that is, if two gases possess the same number 
of particles in a given volume, it is evident that 
one will disperse heat most quickly which has 
its atoms of the least weight ; and if other 
two gases have particles of the same weight, 
that one will most disperse heat which has the 
least number in a given volume ; because the 
resistance will be as the number of particles to 
be moved, in like circumstances. Of the 
gases that have nearly the same number of 
particles in the same volume, are, hydrogen,^ 


carburetted hydrogen, sulphuretted hydrogen, 
nitrous oxide, and carbonic acid. These con- 
duct heat in the order they are written, hy- 
drogen best and carbonic acid worst ; and the 
weights of their ultimate particles increase in 
the same order (see page 73). Of those that 
have their atoms of the same weight and 
their number in a given volume difFerenl, are 
oxygen and carburetted hydrogen : the latter 
has the greater cooling power and the fewer 
particles in a given volume. 



It is a remarkable fact, and has never, I be- 
lieve, been satisfactorily accounted for, that the 
atmosphere in all places and seasons is found 
to decrease in temperature in proportion as 
we ascend, and nearly in an arithmetical 
progression. Sometimes the fact may have 
been otherwise, namely, that the air was 
colder at the surface of the earth than above, 
particularly at the breaking of a frost, I have 
observed it so j but this is evidently the effect 


of great and extraordinary commotion in the 
atmosphere, and is at most of a very short 
duration. What then is the occasion of this 
diminution of temperature in ascending ? Be- 
fore this question can be solved, it may be pro- 
per to consider the defects of the common 
solution. — Air, it is said, is not heated by the 
direct rays of the sun ; which pass through it 
as a transparent medium, without producing 
any calorific effect, till they arrive at the sur- 
face of the earth. The earth being heated, 
communicates a portion to the contiguous at- 
mosphere, whilst the superior strata in pro- 
portion as they are more remote, receive less 
heat, forming a gradation of temperature, 
similar to what takes place along a bar of iron 
when one of its ends is heated. 

The first part of the above solution is pro- 
bably correct : Air, it should seem. Is singular 
in regard to heat ; it neither receives nor dis- 
charges it in a radiant state ; if so, the propaga- 
tion of heat through air must be effected by its 
conducting power, the same as in water. 
Now we know that heat applied to the under 
surface of a column of water is propagated 
upwards with great celerity, by the actual 
ascent of the heated particles : it is equally 
certain too that heated air ascends. From 
these observations it should follow that the 


causes assigned above for the gradual change 
of temperature in a perpendicular column of 
the atmosphere, would apply directly to a 
state of temperature the very reverse of the 
fact ; namely, to one in which the higher the 
ascent or the more remote from the earth the 
higher should be the temperature. 

Whether this reasoning be correct or not, it 
must I think be universally allowed, that the 
fact has not hitherto received a satisfactory 
explanation. I conceive it to be one involving 
a new principle of heat; by which I mean a 
principle that no other phenomenon of nature 
presents us with, and which is not at present 
recognized as such. I shall endeavour in what 
follows to make out this position. 

The principle Is this : The natural equili- 
brium of heat . in an atmosphere, is when 
each atom of air in the same perpejidicular 
column is possessed of the same quantity of 
heat; and consequently, the natural equili- 
brium of heat in an atmosphere is ivhen the 
tejnperature gradually diminishes in ascending. 

That this is a just consequence cannot be 
denied, when we consider that air increases in 
its capacity for heat by rarefaction : when the 
quantity of heat is given or limited, therefore 
the temperature must be regulated by the 


It is an established principle that any body 
on the surface of the earth unequally heated is 
observed constantly to tend towards an equality 
of temperature ; the new principle announced 
above, seems to suggest an exception to this 
law. But if it be examined, it can scarcely 
appear in that light. Equality of heat and 
equality of temperature, when applied to the 
same body in the same state, are found so 
uniformly to be associated together, that we 
scarcely think of making any distinction be- 
tween the two expressions. No one would 
object to the commonly observed law being 
expressed in the^e terms : When any body is 
unequally heated, the equilibrium is found to 
be restored when each particle of the body 
becomes in possession of the same quantity of 
heat. Now the law thus expressed is what I 
apprehend to be the true general law, which 
applies to the atmosphere as well as to other 
bodies. It is an equality of heat, and not an 
equality o^ temperature that nature tends to 

The atmosphere indeed presents a striking 
peculiarity to us in regard to heat : we see in 
a perpendicular column of air, a body without 
any change of form, slowly and gradually 
changing its capacity for heat from a less 


to a greater j but all other bodies retain a 
uniform capacity throughout their substance. 

If it be asked why an equilibrium of heat 
should turn upon the equality in quantity rather 
daan in temperature ; I answer that I do not 
know : but I rest the proof of it upon the fact 
of the inequality of temperature observed in 
ascending into the atmosphere. If the natural 
tendency of the atmosphere was to an equality 
of temperature, there does not appear to me 
any reason why the superior regions of the 
air should not be at least as warm as the 

The arguments already advanced on behalf 
of the priaciple we are endeavouring to 
establish, are powerfully corroborated by the 
following facts : — By the observations of 
Bouguer, Saussure, and Gay Lussac, we find 
that the temperature of the air at an elevation 
where its weight is t that at the surface, is 
about 50° Fahrenheit less than that at the sur- 
face : and from my experiments (Manch. 
Mem. vol. 5. page 525.) it appears that air 
being suddenly rarefied from 2 to 1 produces 
50° of cold. Whence we may infer, that a 
measure of air at the earth's surface being 
taken up to the height above-mentioned, pre- 
serving its original temperature, and suffered 
to expand, would become two measures, and be 


reduced to the same temperature as the sur- 
rounding air ; or viccy versuy if two measures 
of air at the proposed height were condensed 
into one measure, their temperature would be 
raised 50% and they would become the same in 
density and temperature, as the like volume of 
air at the earth's surface. In like manner we 
may infer, that if a volume of air from the 
earth's surface, to the summit of the atmo- 
sphere were condensed and brought inio a 
horizontal position on the earth's surface, it 
would become of the same density and tem- 
perature as the air around it, without receiving 
or parting with any heat whatever. 

Another important argument in favour of 
the theory here proposed may be derived from 
the contemplation of an atmosphere of vapour. 
Suppose the present aerial atmosphere were to 
be annihilated, and one of steam or aqueous 
vapour were substituted in its place ; and sup- 
pose further, that the temperature of this at- 
mosphere at the earth's surface were every 
where 212° and its weight equal to 30 inches 
of mercury. Now at the elevation of about 
6 miles the weight would be 15 inches or 
-I of that below, at 12 miles, it would be 
7.5 inches, or -^ of that at the surface, &c. and 
the temperature would probably diminish 25° 
at each of those intervals. It could not di- 


minisb more; for we have seen (page 14) that 
a diminution of temperature of 25'' reduces 
the force of vapour one half; if therefore a 
greater reduction of temperature were to take 
place, the weight of the incumbent atmosphere 
would condense a portion of the vapour into 
water, and the general equilibrium would 
thus be disturbed perpetually from condensa- 
tions in the upper regions. But if we suppose 
on the other hand, that the diminution of tem- 
perature in each of these intervals is less than 
25% then the upper regions could admit of 
more vapour without condensation ; but it must 
take place at the surface, because vapour at 
212* cannot sustain more than the weight of 
30 inches of mercury. 

These three supposed cases of an aqueous 
vapour atmosphere may be otherwise stated 
thus : 

1. The specific gravity of steam at the earth's 
surface being supposed .6 of atmospheric air, 
and the weight of the atmosphere of steam 
equal to SO inches of mercury, its temperature 
at the surface would be 212°; at 6 miles 
high, 187°; at 12 miles, 162°; at 18 miles, 
137°; at 24 miles, 112°, &c. — In this Case the 
density, not only at the surface, but every 
where, would be a maximum, or the greatest 
possible for the existing temperature ; so that 


a perfect equilibriam having once obtained, 
there could be neither condensation nor eva^- 
poration in any region. For every 400 yards 
of elevation, the thermometer would descend 
I degree. 

2. If the atmosphere were constituted just 
as above, except that the temperature now 
diminished more rapidly than at the rate of 
25° for 6 miles ; then the temperature of the 
higher regions not being sufficient to support 
the weight, a condensation must take place j 
the weight would thus be diminished, but as 
the temperature at the surface is always sup- 
posed to be kept at 212°, evaporation must go 
on there with the design to keep up the pres- 
sure at 30 inches. Thus there would be per- 
petual strife between the recently raised vapour 
ascending, and the condensed drops of rain 
descending. A position much less likely than 
the preceding one. 

3. The same things being supposed as be- 
fore, but now the temperature decreases more 
slowly than at the rate of 25° for 6 miles : in 
this case the density of the steam at the earth's 
surface would be a maximum for the tempera- 
ture, but no where else ; so that if a quantity of 
water were taken up to any elevation it would 
evaporate -, but the increased weight of the 
atmosphere would produce a condensation of 


Steam into water on the ground. In this case 
then there would not be that equilibrium, 
which we see in the 1st case, and which ac- 
cords so much more with the regularity and 
simplicity generally observable in the laws of 

* I owe to Mr. Ewart the first hint of the idea respect- 
ing elastic fluidii, which I have endeavoured to expand 
in the present section ; he suggested to me some time ago, 
that it was probable steam of any low temperature, as 32", 
of maximum density, contained the same quantity of ab- 
solute heat as the like weight of steam of 212* of maximum 
density; and that consequently if it could be gradually 
compressed without losing any heat, that is, if the con- 
taing vessel kept pace with it in increase of temperature, 
there would never be any condensation of steam into water, 
but it would constantly retain its elasticity. 

In fact the heat (1000<'), which is given out by steam 
when it is condensed into water, is merely heat of com- 
pression; there is no change in the affinity of the molecules 
of water for heat ; the expulsion is occasioned solely by 
the approximation of the molecules, and would be precisely 
the same whether that approximation was occasioned by ex- 
ternal compression or internal attraction. Indeed if we estimate 
the temperature thai would be given out by the mechanical 
compression of steam from a volume of 2048 to that of 1, by 
successively doubling the density, and supposing as above, 
that at each time of doubling, 25° were given out, it 
would be found that 12 successive operations would reduce 
the volume to J, and that only 300" would be given out. 
But it is not right to conclude, that the same quantity of 
temperature would be given out at each of the successive 


That an atmosphere of steam does actually 
surround the earth, existing independently of 
the other atmospheres with which however it 
is necessarily most intimately mixed, is I think 
capable of dcmonsti*ation. I have endeavoured 
to enforce and illustrate it in several Essays in 
the Memoirs of the Manchester Society, and 
in Nicholson's Journal, to which I must refer. 
Now an atmosphere of any elastic fluid, 
whether of the weight of 30 inches of mer- 
cury, or of half an inch, must observe the same 
general laws ; but it should seem that an 
atmosphere of vapour varies its temperature 

condensations, though it may be nearly so for most of them : 
towards the conclusion, the space occupied by the solid 
atom or particle bears a considerable proportion to the whole 
space occupied by it and its atmosphere. At the first com- 
pression, the atmosphere of heat might be said to be re- 
duced into half the space ; but at the last, the reduction 
would be much greater, and therefore more heat given out 
than determined by theory. 

Since writing the above, Mr. Ewart informs me that the 
idea respecting steam, which I had from him, is originally 
Mr. Watt*3. In Black's Lectures, Vol. 1, page 190, the 
author, speaking of Mr. Watt's experiments on steam at 
low temperatures, observes, " we find that the latent heat 
of the steam is at least as much increased as the sensible 
heat is diminished." It is wonderful that so remarkable a 
fact should have been so long known and so little noticed. 


less rapidly in ascending than the one we have 
of air. Something of an effect similar to what 
is pointed out in the 2d case above, ought 
therefore to be observed in our mixed at- 
mosphere ; — namely, a condensation of vapour 
in the higher regions, at the same moment 
that evaporation is going on below. — This is 
actually the case almost every day, as all know 
from their own observation ; a cloudy stratum 
of air frequently exists above, whilst the 
region below is comparatively dry. 



Several remarkable phenomena are attend- 
ant upon the congelation of water, and some 
of them are so different from what might be 
expected from analogy, that I believe no ex- 
planation according with the principles of the 
mechanical philosophy has been attempted, 
such as to account for all the appearances. 
This attempt is the object of the present 
Essay. It will be expedient previously to state 
the principal facts. 


1 . The specific gravity of ice is less than that 
of water in the ratio of 92 to 100. 

2. When water is exposed in a large sus- 
pended jar to cool in still air of 20 or 30% it 
may be cooled 2 or 3° below freezing ; but if 
any tremulous motion take place, there appear 
instantly a multitude of shining hexangular 
spicul(Cy floating, and slowly ascending in the 

3. It is observed that the shoots or ramifica- 
tions of ice at the commencement, and in the 
early stage of congelation are always at an 
angle of 60 or 120% 

4. Heat is given out during congelation, as 
much as would raise the temperature of water 
150° of the new scale. The same quantity is 
again taken in when the ice is melted. This 
quantity may be ^V of t^e whole heat which 
water of 32° contains. 

5. Water is densest at 36° of the old scale, 
or 38° of the new : from that point it gradu- 
ally expands by cooling or by heating alike, 
according to the law so often mentioned, that 
of the square of the temperature. 

6. If water be exposed to the air, and to 
agitation, it cannot be cooled below 32° ; the 
application of cold freezes a part of the water, 
and the mixture of ice and water requires the 
temperature of 32°. 


7. If the water be kept still, and the cold be 
not severe, it may be cooled in large quantities 
to 25° or below, without freezing ; if the water 
be confined in the bulb of a thermometer, it is 
very difficult to freeze it by any cold mixture 
above 15° of the old scale; but it is equally 
difficult to cool the water much below that 
temperature without its freezing. I have ob- 
tained it as low as 7 or 8% and gradually heated 
it again without any part of it being frozen. 

8. In the last case of what may be called 
forced cooling, the law of expansion is still 

observed as given above, 

9. When water is cooled to 15° or below in 
a bulb, it retains the most perfect transparency ; 
but if it accidentally freeze, the congelation 
is instantaneous, the bulb becoming in a mo- 
ment opake and white like snow, and the 
water is projected up the stem. 

10. When water is cooled below freezing, 
and congelation suddenly takes place, the tem- 
perature rises instantly to 32°. 

In order to explain these phenomena, let it 
be conceived that the ultimate or smallest ele- 
ments of water are all globular, and exactly 
of the same size ; let the arrangement of these 
atoms be in squares, as exhibited in Fig, 1. 
Plate 3. so that each particle touches four others 
in the same horizontal plane. Conceive a second 


Stratum of particles placed upon these in like 
order of squares, but so that each globule falls 
into the concavity of four others on the first 
stratum, and consequently rests upon four 
points, elevated 45° above the centres of the 
globules. A perpendicular section of such 
globule resting upon two diagonal globules of 
the square is exhibited in Fig. 3. Conceive 
a third stratum placed in like manner upon the 
second, &c. The whole being similar to a 
square pile of shot. — 'The above constitution 
is conceived to represent that of water at the 
temperature of greatest density. 

To find the number of globules in a cubic 
vessel, the side of which is given ; let n = the 
number of particles in one line or side of the 
cube ; then 7i* is the number in any horizontal 
stratum ; and because a line joining the centres 
of two contiguous particles in different strata 
makes an angle of 45° with the horizontal 
plane, the number of strata in the given 
height will be n -r- sine of 45° =^ n -r- \\/2. 
Whence the number of particles in the cubic 
vessel = 7i^ -r- f ^2 — n^yj 2. 

Now let it be supposed that the square pile 
is instantly drawn into the shape of a rhombus 
(Fig2.) ; then each horizontal stratum will still 
consist of the same number of particles as be- 
fore, only in a more condensed form, each 


particle being now in contact with six others. 
But to counteract this condensation, the se- 
veral successive strata are more elevated than 
before, so that the pile is increased in height. 
A question then arises whether a vessel of 
given capacity will hold a greater number of 
particles in this or the former disposition ? It 
must be observed, that in the last case, each 
particle of a superior stratum rests only on two 
particles of an inferior one, and is therefore 
elevated by the sine of 60' as represented in 
Fig. 4. The bases of the two piles are as 
1 : ^/l> and their heights as Vf - Vt ^^^ ^^^ 
capacities are as the products of tlie base and 
height, or as yf\ : \'y that is, as .707 to .750 
nearly, or as 94 to 100, Thus it appears that 
the first arrangement contains more particles 
in a given space than the second by 6 per 

The last or rhomboidal arrangement is sup- 
posed to be that which the particles of water 
assume upon congelation. The specific gra- 
vities of ice and water should therefore be as 
94 to 100. But it should be remembered 
that water usually contains 2 per cent, in bulk 
of atmospheric air : and that this air is liberated 
upon congelation ; and is commonly entangled 
amongst the ice in such sort as to increase its 
bulk without materially increasing its weight ; 


this reduces the specific gravity of ice 2 per 
cent, or makes it 92, which agrees exactly 
with observation. Hence the 1st fact is ex- 

The angle of a rhombus is 60% and its sup- 
plement 120°; if any particular angles are 
manifested in the act of congelation, therefore 
we ought to expect these, agreeable to the 
2d and 3d phenomena. 

Whenever any remarkable change in the 
internal constitution of any body takes place, 
whether by the accession and junction of new 
particles, or by new arrangements of those 
already existing in it ; some modification in 
the atmospheres of heat must evidently be re- 
quired ; though it may be difficult to estimate 
the quantity, and sometimes even the kind of 
change so produced, as in the present case. 
So far therefore the theory proposed agrees 
with the 4th phenomenon. 

In order to explain the other phenomena, it 
will be requisite to consider more particularly 
the mode by which bodies are expanded by 
heat. — Is the expansion occasioned simply by 
the enlargement of the individual atmospheres 
of the component particles ? This is the case 
with elastic fluids, and perhaps with solids, 
but certainly not with liquids. How is it pos- 
sible that water should be expanded a portion 


represented by l upon the addition of a cer- 
tain quantity of heat at one temperature, and 
by 340 upon the addition of a like quantity at 
another temperature, when both temperatures 
are remote from the absolute zero, the one 
perhaps 6000° and the other 6170° ? The 
fact cannot be accounted for on any other sup- 
position than that of a change of arrangement 
in the component particles ; and a gradual 
change from the square to the rhomboidal ar- 
rangement is in all probability effected both 
by the addition and abstraction of heat. It is to 
be supposed then that water of the greatest 
possible density has its particles arranged in 
the square form ; but if a given quantity of 
heat be added to, or taken from it, the par- 
ticles commence their approach to the rhom- 
boidal form, and consequently the whole is 
expanded, and that the same by the same 
change of temperature, whether above or 
below that point. 

If heat be taken away from water of 38°, 
then expansion is the consequence, and a mo- 
derate inclination of the particles towards the 
rhomboidal form; but this only extends a 
small way whilst the mass is subject to a 
tremulous motion, so as to relieve the obstruc- 
tions occasioned by friction ; by the energy 
of certain affinities, the new form is completed 


in moment, and a portion of ice formed ; heat 
is then given out which retards the subsequent 
formation, till at last the whole is congealed. 
This is the ordinary process of congelation. 
But if the mass of water cooled is kept in a 
state of perfect tranquillity, the gradual ap- 
proach to the rhomboidal form can be carried 
much farther ; the expansion goes on accord- 
ing to the usual manner, and the slight friction 
or adhesion of the particles is sufficient to 
counteract the balance of energies in favour of 
the new formation, till some accidental tremor 
contributes to adjust the equilibrium. A 
similar operation is performed when we lay a 
piece of iron on a table, and hold a magnet 
gradually nearer and nearer ; the proximity of 
the approach, without contact, is much assisted 
by guarding against any tremulous motion of 
the table. Hence the rest of the phenomena 
are accounted for. 

{ 141 ) 




HERE are three distinctions in the kindsof 
bodies,or three states,which have more especially 
claimed the attention of philosophical chemists; 
namely, those which are marked by the terms 
elastic Jiuids^ liquids^ and solids. A very fa- 
miliar instance is exhibited to us in water, of 
a body, which, in certain circumstances, is 
capable of assuming all the three states. In 
steam we recognise a perfectly elastic fluid, 
in water, a perfect liquid, and in ice a com- 
plete solid. These observations have tacitly 
led to the conclusion which seems universally 
adopted, that all bodies of sensible magnitude, 
■whether liquid or solid, are constituted of a 
vast number of extremely small particles, or 
atoms of matter bound together by a force of 
attraction, which is more or less powerful 
according to circumstances, and which as it 
endeavours to prevent their separation, is very 


properly called in that view, atlraction of 
cohesion ; but as it collects them from a dis- 
persed state (as from steam into water) it is 
called, attraction of aggregation^ or more 
simply, affinity. Whatever names it may go 
by, they still signify one and the same power. 
It is not my design to call in question this con- 
clusion, which appears completely satisfactory ; 
but to shew that we have hitherto made no 
use of it, and that the consequence of the 
neglect, has been a very obscure view of 
chemical agency, which is daily growing more 
so in proportion to the new lights attempted 
to be thrown upon it. 

The opinions I more particularly allude to, 
are those of Berthollet on the Laws of che- 
mical affinity ; such as that chemical agency is 
proportional to the mass, and that in all che- 
mical unions, there exist insensible gradations 
in the proportions of the constituent principles. 
The inconsistence of these opinions, both 
with reason and observation, cannot, I think, 
fail to strike every one who takes a proper 
view of the phenomena. 

Whether the ultimate particles of a body, 
such as water, are all alike, that is, of the 
same figure, weight, &c. is a question of some 
importance. From what is known, we have 
no reason to apprehend a diversity in these 


particulars : if it does exist in water, it must 
equally exist in the elements constituting water, 
namely, hydrogen and oxygen. Now it is 
scarcely possible to conceive how the aggre- 
gates of dissimilar particles should be so uni- 
formly the same. If some of the particles of 
water were heavier than others, if a parcel 
of the liquid on any occasion were constituted 
principally of these heavier particles, it must 
be supposed to affect the specific gravity of the 
mass, a circumstance not known. Similar ob^ 
servations may be made on other substances. 
Therefore we may conclude that the ultimate 
particles of all homogeneous bodies are per- 
fectly alike in weight, fgure, ^c. In other 
words, every particle of water is like every 
other particle of water , every particle of hy- 
drogen is like every other particle of hydro- 
gen, &c. 

Besides the force of attraction, which, in 
one character or another, belongs universally to 
ponderable bodies, we find another force that 
is likewise universal, or acts upon all matter 
which comes under our cognisance, namely, a 
force of repulsion. This is now generally, 
and I think properly, ascribed to the agency of 
heat. An atmosphere of this subtile fluid 
constantly surrounds the atoms of all bodies, 
and prevents them from being drawn into 


actual contact. This appears to be satisfac- 
torily proved by the observation, that the bulk 
of a body may be diminished by abstracting 
some of its heat: But from what has been 
stated in the last section, it should seem that 
enlargement and diminution of bulk depend 
perhaps more on the arrangement, than on the 
size of the ultimate particles. Be this as it 
may, we cannot avoid inferring from the pre- 
ceding doctrine on heat, and particularly from 
the section on the natural zero of temperature, 
that solid bodies, such as ice, contain a large 
portion, perhaps 4- of the heat which the 
same are found to contain in an elastic state, 
as steam. 

We are now to consider how these two 
great antagonist powers of attraction and re» 
pulsion are adjusted, so as to allow of the three 
different states of clastic Jiiiids^ liquids^ and 
solids. We shall divide the subject into four 
Sections ; namely, first, on the constitution of 
pure elastic Jluids ; second, on the constitution 
of mixed elastic fluids ; third, on the constitu- 
tion of liquids f and fourth, on the constitution 
of solids. 




A pure elastic fluid is one, the constituent 
particles of which are all alike, or in no way 
distinguishable. Steam, or aqueous vapour, 
hydrogenous gas, oxygenous gas, azotic gas,* 
and several others are of this kind. These 
fluids are constituted of particles possessing 
very diffuse atmospheres of heat, the capacity 
or bulk of the atmosphere being often one or 
two thousand times that of the particle in a 
liquid or solid form. Whatever therefore may 
be the shape or figure of the solid atom ab- 
stractedly, when surrounded by such an at- 
mosphere it must be globular ; but as all the 
globules in any small given volume are subject 
to the same pressure, they must be equal in 
bulk, and will therefore be arranged in hori- 
zontal strata, like a pile of shot. A volume 

* The novice will all along understand that several 
chemical subjects are necessariiy introduced before their 
general history and character can be discussed. 


of elastic fluid is found to expand whenever the 
pressure is taken off. This proves that the re- 
pulsion exceeds the attraction in such case. 
The absolute attraction and repulsion of the 
particles of an elastic fluid, we have no means 
of estimating, though we can have little doubt 
but that the cotemporary energy of both is great; 
but the excess of the repulsive energy above 
the attractive can be estimated, and the law of 
increase and diminution be ascertained in many 
cases. Thus in steam, the density may be 
taken at tAt ^^'^^ ^^ water ; consequently 
each particle of steam has 12 times the diameter 
that one of water has, and must press upon 
144 particles of a watery surmce; but the 
pressure upon each is equivalent to that of a 
column of water of 34 feet ; therefore the ex- 
cess of the elastic force in a particle of steam is 
equal to the weight of a column of particles of 
water, whose height is 34 X 144 = 4896 feet , 
And further, this elastic force decreases as the 
distance of the panicles increases. With re- 
spect to steam and other elastic fluids then, 
the force of cohesion is entirely counteracted 
by that of repulsion, and the only force which 
is efficacious to move the particles is the excess 
of the repulsion above the attraction. Thus, if 
the attraction be as 10 and the repulsion as 
12, the effective repulsive force is as 2. It 


appears then, that an elastic fluid, so far from 
requiring any force to separate its particles, it 
always requires a force to retain them in their 
situation, or to prevent their separation. 

A vessel full of any pure elastic fluid presents 
to the imagination a picture like one full ofsmall 
shot. The globules are all of the same size j 
but the particles of the fluid differ from those 
of the shot, in that they are constituted of an 
exceedingly small central atom of solid mat- 
ter, which is surrounded by an atmosphere of 
heat, of great density next the atom, but 
gradually growing rarer according to some 
power of the distance ; whereas those of the 
shot are globules, uniformly hard throughout, 
and surrounded w^ith atmospheres of heat of 
no comparative magnitude. 

It is known from experience, that the force 
of a mass of elastic fluid is directly as the 
density. Whence is derived the law already 
mentioned, that the repulsive power of each 
particle is inversely as its diameter. That is, 
the apparent repulsive power, if we may so 
speak ; for the real or absolute force of re- 
pulsion is not known, as long as we remain 
ignorant of the attractive force. When we 
expand any volume of elastic fluid, its particles 
are enlarged, without any material change in 
the quantity of their heatj it follows then, that 


the density of the atmospheres of heat must 
fluctuate with the pressure. Thus, suppose a 
measure of air were expanded into 8 measures ; 
tlien, because the diameters of the elastic par- 
ticles are as the cube root of the space, the 
distances of the particles would be twice as 
great as before, and the elastic atmospheres 
would occupy nearly 8 times the space they 
did before, with nearly the same quantity of 
heat : whence we see that these atmospheres 
must be diminished in density in nearly the 
same ratio as the mass of elastic fluid. 

Some elastic fluids, as hydrogen, oxygen, &c. 
resist any pressure that has yet been applied 
to them. In such then it is evident the re- 
pulsive force of heat is more than a match for 
the affinity of the particles, and the external 
pressure united. To what extent this would 
continue we cannot say j but from analogy we 
might apprehend that a still greater pressure 
would succeed in giving the attractive force 
the superiority, when the elastic fluid would 
become a liquid or solid. In other elastic 
fluids, as steam, upon the application of com- 
pression to a certain degree, the elasticity ap- 
parently ceases altogether, and the particles 
collect in small drops of liquid, and fall down. 
This phenomenon requires explanation. 

From the very abrupt transition of steam 


from a volume of 1700 to that of 1, without 
any material increase of pressure, one would 
be inclined to think that the condensation of 
it was owing to the breaking of a spring, rather 
than to the curbing of one. The last however 
I believe is the fact. The condensation arises 
from the action of affinity becoming superior 
to that of heat, by which the latter is over* 
ruled, but not weakened. As the approxima- 
tion of the particles takes place, their repulsion 
increases from the condensation of the heat, 
but their affinity increases, it should seem^ in a 
still greater ratio, till the approximation has at- 
tained a certain degree, when an equilibrium 
between those two powers takes place, and 
the liquid, water, is the result. That this is the 
true explanation we may learn from what has 
been stated at page 131; wherein it is shewn 
that the heat given off by the condensation of 
steam, is in all probability no more than would 
be given off by any permanently elastic fluid, 
could it be mechanically condensed into the 
like volume, and is moreover a small portion 
of the whole heat previously in combination. 
As far then as the heat is concerned in this 
phenomenon, the circumstances would be the 
same, whether the approximation of the par- 
ticles was the effect of affinity, or of external 
mechanical force. 


The constitution of a liquid, as water, must 
then be conceived to be that of an aggregate of 
particles, exercising in a most powerful manner 
the forces of attraction and repulsion, but 
nearly in an equal degree. — Of this more in 
the sequel. 



When two or more elastic fluids, whose 
particles do not unite chemically upon mixture, 
are brought together, one measure of each, 
they occupy the space of two measures, but 
become uniformly diffused through each other, 
and remain so, whatever may be their specific 
gravities. The fact admits of no doubt j but 
explanations have been given in various ways, 
and none of them completely satisfactory. As 
the subject is one of primary importance in 
forming a system of chemical principles, we 
must enter somewhat more fully into the 

Dr. Priestley was one of the earliest to notice 
the fact : it naturally struck him with surprise. 


that two elastic fluids, having apparently no 
affinity for each other, should not arrange 
themselves according to their specific gravities, 
as liquids do in like circumstances. Though 
he found this was not the case after the elastic 
fluids had once been thoroughly mixed, yet he 
suggests it as probable, that if two of such 
fluids could be exposed to each other without 
agitation, the one specifically heavier would 
retain its lower situation. He does not so 
much as hint at such gases being retained in a 
mixed state by affinity. With regard to his 
suggestion of two gases being carefully ex- 
posed to each other without agitation, I made 
a series of experiments expressly to determine 
the question, the results of which are given in 
the Manch. Memoirs, Vol. 1. new series. 
From these it seems to be decided that gases 
always intermingle and gradually diffuse them- 
selves amongst each other, if exposed ever so 
carefully ; but it requires a considerable time 
to produce a complete intermixture, when 
the surface of communication is small. This 
time may vary from a minute, to a day or more, 
according to the quantity of the gases and the 
freedom of communication. 

When or by whom the notion of mixed gases 
being held together by chemical affinity was 
first propagated, I do not know ; but it seems 


probable that the notion of water being dis' 
solved in air, led to that of air being dissolved 
in air. — Philosophers found that water gra- 
dually disappeared or evaporated in air, and 
increased its elasticity; but steam at a low 
temperature was known to be unable to over- 
come the resistance of the air, therefore the 
agency of affinity was necessary to account for 
the effect. In the permanently elastic fluids 
indeed, this agency did not seem to be so much 
wanted, as they are all able to support them- 
selves; but the diffusion through each other 
was a circumstance which did not admit of an 
easy solution any other way. In regard to th« 
solution of water in air, it was natural to sup- 
pose, nay, one might almost have been satisfied 
without the aid of experiment, that the differ- 
ent gases would have had different affinities for 
water, and that the quantities of water dis- 
solved in like circumstances, would have 
varied according to the nature of the gas. 
Saussure found however that there was no 
difference in this respect in the solvent powers 
of carbonic acid, hydrogen gas, and common 
air. — It might be expected that at least the 
density of the gas would have some influence 
upon its solvent powers, that air of half density 
would take half the water, or the quantity of 
water would diminish in some proportion to 


the density; but even here again we are 
disappointed ; whatever be the rarefaction, if 
water be present, the vapour produces the 
same elasticity, and the hygrometer finally 
settles at extreme moisture, as in air of com- 
mon density in like circumstances. These 
facts are sufficient to create extreme difficulty 
in the conception how any principle of affinity 
or cohesion between air and water can be the 
agent. It is truly astonishing that the same 
quantity of vapour should cohere to one particle 
of air in a given space, as to one thousand in 
the same space. But the wonder does not 
cease here ; a torricellian vacuum dissolves wa- 
ter; and in this instance we have vapour existing 
independently of air at all temperatures ; what 
makes it still more remarkable is, the vapour 
in such vacuum is precisely the same in quan-^ 
tlty and force as in the like volume of any 
kind of air of extreme moisture. 

These and other considerations which oc- 
curred to me some years ago, were sufficient to 
make me altogether abandon the hypothesis of 
air dissolving water, and to explain the phe- 
nomena some other way, or to acknowledge 
they were inexplicable. In the autumn of 
1801, I hit upon an idea which seemed to be 
exactly calculated to explain the phenomena 
of vapour ; it gave rise to a great variety of 


experiments upon which a series of essays were 
founded, which were read before the Literary 
and Philosophical Society of Manchester, and 
published in the 5th Vol. of their memoirs, 

The distinguishing feature of the new 
theory was, that the parti 'les of one gas are 
not elastic or repulsive in regard to the par- 
ticles of another gas, but only to the particles 
of their own kind. Consequently when a 
vessel contains a mixture of two such elastic 
fluids, each acts independently upon the vessel, 
with its proper elasticity, just as if the other 
were absent, whilst no mutual action between 
the fluids themselves is observed. This posi- 
tion most effectually provided for the existence 
of vapour of any temperature in the atmos- 
phere, because it could have nothing but its 
own weight to support ; and it was perfectly 
obvious why neither more nor less vapour couid 
exist in air of extreme moisture, than in a 
vacuum of the same temperature. So far then 
the great object of the theory was attained. 
The law of the condensation of vapour in the 
atmosphere by cold, was evidently the same on 
this scheme, as that of the condensation of 
pure steam, and experience was found to con- 
firm the conclusion at all temperatures. The 
only thing now wanting to completely establish 


the independent existence of aqueous vapour 
in the atmosphere, was the conformity of other 
liquids to water, in regard to the diffusion 
and condensation of their vapour. This was 
found to take place in several liquids, and 
particularly in sulphuric ether, one which was 
most likely to shew any anomaly to advantage 
if it existed, on account of the great change of 
expansibility in its vapour at ordinary tern* 
peratures. The existence of vapour in the 
atmosphere and its occasional condensatioQ 
were thus accounted for ; but another 
question remained, how does it rise from 
a surface of water subject to the pressure 
of the atmosphere ? The consideration of 
this made no part of the essays abovementioned, 
it being apprehended, that if the other two 
points could be obtained by any theory, this 
third too, would, in the sequel, be accom- 

From the novelty, both in the theory and the 
experiments, and their importance, provided 
they were correct, the essays were soon circu- 
lated, both at home and abroad. The new 
facts and experiments were highly valued, 
some of the latter were repeated, and found 
correct, and none of the results, as far as I 
know, have been controverted; but the theory 
was almost universally misunderstood, and 


consequently reprobated. This must have 
have arisen partly at least from my being too 
concise, and not sufficiently clear in its ex- 

Dr. Thomson was the first, as far as I know, 
who publicly animadverted upon the theory ; 
this gentleman, so well known for his excellent 
System of Chemistry, observed in the first 
edition of that work, that the theory would 
not account for the equal distribution of gases j 
but that, granting the supposition of one gas 
neither attracting nor repelling another, the two 
must still arrange themselves according to their 
specific gravity. But the most general objec- 
tion to it was quite of a different kind ; it was 
admitted, that the theory was adapted so as to 
obtain the most uniform and permanent diffusion 
of gases j but it was urged, that as one gas 
was as a vacuum to another, a measure of any 
gas being put to a measure of another, the 
two measures ought to occupy the space of 
one measure only. Finding that my views on 
the subject were thus misapprehended, I 
wrote an illustration of the theory, which was 
published in the 3d Vol. of Nicholson's Jour- 
nal, for November, 1802. In that paper I 
endeavoured to point out the conditions of 
mixed gases more at large, according to my 
hypothesis ; and particularly touched upon the 


discriminating feature of it, that of two par- 
ticles of any gas A, repelling each other by 
the known stated law, whilst one or more 
particles of another gas B, were interposed in 
a direct line, without at all affecting the re- 
ciprocal action of the said two particles of A. 
Or, if any particle of B were casually to come 
in contact with one of A, and press against it, 
this pressure did not preclude the cotemporary 
action of all the surrounding particles of A 
upon the one in contact with B. In this re- 
spect the mutual action of particles of the same 
gas was represented as resembling magnetic 
action, which is not disturbed by the interven- 
tion of a body not magnetic. 

As the subject has since received the ani- 
madversions of several authors, which it is 
expedient to notice more or less, it will be 
proper to point out the order intended to be 
pursued. First, I shall consider the objections 
to the new theory made by the several authors, 
with their own views on the subject ; and 
then shall give what modifications of the 
theory, the experience and reflection of suc- 
ceeding time have suggested to me. The 
authors are BerthoUet, Dr. Thomson, Mr. 
Murray, Dr. Henry, and Mr. Gough. 

BerthoUet in his Chemical Statics (1804) 
has given a chapter on the constitution of the 


atQiosphere, in which he has entered largely 
into a discussion of the new theory. This cele- 
brated chemist, upon comparing the results of 
experiments made by De Luc, Saussure, Volta, 
Lavoisier, Watt, &c. together with those of 
Gay Lussac, and his own, gives his full assent 
to the fact, that vapours of every kind increase 
the elasticity of each species of gas alike, and 
just as much as the force of the said vapours 
in vacuo ; and not only so, but that the specific 
gravity of vapour in air and vapour in vacuo 
is in all cases the same (Vol. 1. Sect. 4.) Con- 
sequently he adopts the theorem for finding 
the quantity of vapour which a given volume 
of air can dissolve, which I have laid down ; 

where p represents the pressure upon a given 
volume (1) of dry air, expressed in inches of 
mercury, /= the force of the vapour in vacuo 
at the temperature, in inches of mercury, and 
5 r= the space which the mixture of air and 
vapour occupies under the given pressure, />, 
after saturation. So far therefore we perfectly 
agree : but he objects to the theory by which 
I attempt to explain these phenomena, and 
substitutes another of his own. 

The first objection I shall notice is one that 


clearly shews Berthollet either does not under- 
stand, or does not rightly apply the theory he 
opposes ; he says, " If one gas occupied the 
interstices of another, as though they were 
vacancies, there would not be any augmenta- 
tion of volume when aqueous or ethereal va- 
pour was combined with the air; nevertheless 
there is one proportional to the quantity of 
vapour added : humidity should increase the 
specific gravity of the air, whereas it renders 
it spyecifically lighter, as has been already 
noticed by Newton." This is the objection 
which has been so frequently urged ; it has 
even been stated by Mr. Gough, if I under- 
stand him aright, in almost the same words 
(Nicholson's Journal, Vol. 9, page 162) ; yet 
this last gentleman is profoundly skilled in 
the mechanical action of fluids. Let a tall 
cylindrical glass vessel containing drv air be 
inverted over mercury, and a portion of the 
air drawn out by a syphon, till an equilibrium 
of pressure is established within and without ; 
let a small portion of water, ether, &c. be 
then thrown up into the vessel ; the vapour 
ris€s and occupies the interstices of the air as 
a void; but what is the obvious consequence? 
Why, the surface of the mercury being now 
pressed both by the dry air, and by the new 
raised vapour, is more pressed within than 


without, and an enlargement of the volume of 
air is unavoidable, in order to restore the 
equilibrium. Again, in the open air: suppose 
there were no aqueous atmosphere around the 
earth, only an azotic one = 23 inches of mef". 
cury, and an oxygenous one = 6 inches. The 
air being thus perfectly dry, evaporation would 
commence with great speed. The vapour 
first formed being constantly urged to ascend 
by that below, and as constantly resisted by the 
air, must, in the first instance, dilate the other 
two atmospheres j (for, the ascending steam 
adds its force to the upward elasticity of the 
two gases, and in part alleviates their pressure, 
the necessary consequence of which is dilata- 
tion.) At last when all the vapour has as- 
cended, that the temperature will admit of, 
the aqueous atmosphere attains an equilibrium j 
it no longer presses upon the other two, but 
upon the earth ; the others return to their 
original density and pressure throughout. In 
this case it is true, there would not be any 
augmentation of volume when aqueous vapour 
was combined with the air; humidity would 
increase the weight of the congregated atmo- 
spheres,but diminish their specific gravity under 
a given pressure. One would have thought that 
this solution of the phenomenon upon my 
hypothesis was too obvious to escape the notice 


of any one in any degree conversant with 
pneumatic chemistry. Berthollet indeed en- 
quires, " Is such a divsion of the same pressure 
of the atmosphere analogous with any physical 
property yet known ? Can it be conceived that 
an elastic substance exists, which adds its 
volume to that of another, and which never- 
theless does not act on it by its expansive 
force ?" Certainly ; we can not only conceive 
it, but bring an instance that must be allowed 
to be in point. Two magnets repel each 
other, that is, act upon each other with an ex- 
pansive force, yet they do not act upon other 
bodies in the same way, but merely as inelastic 
bodies ; and this no doubt would be the same 
if they were reduced to atoms : So two par- 
ticles of the same kind of air may act upon 
each other elastically, and upon other bodies 
inelastically, and therefore not at all, unless 
when in contact. 

Berthollet observes, " Hydrogen gas and 
oxygen gas form water in a given circumstance; 
azotic gas, and oxygen gas, can also produce 
nitric acid ; but the reciprocal action which 
decides the combinations cannot be considered 
as a force commencing at the precise moment 
at which it is manifested, it must have existed 
long before producing its effect, and increases 
gradually till it becomes preponderant." It is 


no doubt true that the opposite powers of at- 
traction and repulsion are frequently, perhaps 
constantly, energetic at the same instant ; but 
the effect produced in those cases arises from 
the difference of the two powers. When the 
excess of the repulsive power above the at- 
tractive in different gases is comparatively 
small and insignificant, it constitutes that cha- 
racter which may be denominated neutral, and 
which I supposed to exist in the class of mixed 
gases which are not observed to manifest any 
sign of chemical union. I would not be un- 
derstood to deny an energetic affinity between 
oxygen and hydrogen, &c. in a mixed state ; 
but that affinity is more than counterbalanced 
by the repulsion of the heat, except in cir- 
cumstances which it is not necessary at present 
to consider. 

Again, " Azotic gas comports itself with 
oxygen gas, in the changes occasioned by tem- 
perature and pressure, precisely like one and 
the same gas : Is it necessary to have recourse 
to a supposition which obliges us to admit so 
great a difference of action without an osten- 
sible cause ?" It is possible this may appear 
an objection to a person who does not under- 
stand the theory, but it never can be any to 
one who does. If a mixture of gas, such as 
atmospheric air, containing azote pressing 


with a force equal to 24 inches of mercury, 
and oxygen with a force equal to 6 inches, 
were suddenly condensed into half the com- 
pass, the azotic gas would then evidently, on 
my hypothesis, press with a force = 48 
inches, and the oxygen with a force =12 
inches, making together 60 inches, just 
the same as any simple gas. And a similar 
change in the elasticity of each would take 
place by heat and cold. Will the opposite 
theory of Berthollet be equally free from this 
objection ? We shall presently examine if. 

Another objection is derived from the very 
considerable time requisite for a body of hy- 
drogen to descend into one of carbonic acid ; 
if one gas were as a vacuum for another, why 
is the equilibrium not instantly established ? 
This objection is certainly plausible j we shall 
consider it more at large hereafter. 

In speaking of the pressure of the atmo- 
sphere retaining water in a liquid state, which I 
deny, Berthollet adopts the idea of Lavoisier, 
" that without it the moleculae would be in- 
finitely dispersed, and that nothing would 
Hmit their separation, unless their own weight 
should collect them to form an atmosphere." 
This, I may remark, is not the language dic- 
tated by a correct notion on the subject. Sup- 
pose our atmosphere were annihilated, and the 


waters on the surface of the globe were in- 
stantly expanded into steam ; surely the action 
of gravity would collect the moleculs into an 
atmosphere of similar constitution to the one 
we now possess ; but suppose the whole mass 
of water evaporated amounted in weight to 
30 inches of mercury, how could it support its 
own weight at the common temperature ? It 
would in a short time be condensed into water 
merely by its weight, leaving a small portion, 
such as the temperature could support, amount* 
ing perhaps to half an inch of mercury in 
weight, as a permanent atmosphere, which 
would effectually prevent any more vapour 
from rising, unless there were an increase of 
temperature. Does not every one know that 
water and other liquids can exist in a Torricel- 
lian vacuum at low temperatures solely by the 
pressure of vapour arising from them ? What 
need then of the pressure of the atmosphere in 
order to prevent an excess of vapourisation? 

After having concluded that " without the 
pressure of the aerial atmosphere, liquids would 
pass to the elastic state," Berthollet proceeds 
in the very next paragraph to shew that the 
quantity of vapour in the atmosphere may in 
fact be much more than would exist if the 
atmosphere were suppressed, and hence infers, 
" that the variations of the barometer oo 


casioned by those of the humidity of the at- 
mosphere may be much greater than was be- 
lieved by Saussure and Deluc." I cannot see 
how the author reconciles the opposite con- 

The experiments of Fontana on the distil- 
lation of water and ether in close vessels con- 
taining air, are adduced to prove, that vapours 
do not penetrate air without resistance. This 
is true no doubt ; vapour cannot make its way 
in such circumstances through a long and 
circuitous route without time, and if the ex- 
ternal atmosphere keep the vessel cool, the 
vapour may be condensed by its sides, and 
fall down in a liquid form as fast as it is ge- 
nerated, without ever penetrating in any sen- 
sible quantity to its remote extremity. 

We come now to the consideration of that 
theory which Berthollet adopts in his explanar 
tionof the phenomena of gaseous mixtures. Ac- 
cording to his theory, there are two degrees of 
affinity. The one is strong, makes the particles of 
bodies approach nearer to each other,and gene- 
rally expels heat : the effect of this may be cal- 
led combinaiio7i ; for instance, when oxygen gas 
is put to nitrous gas, the two combine, give 
out heat, are condensed in volume, and become 
possessed of properties diflerent from what 
they had previously. The other is weak ; it 


does not sensibly condense the volume of any 
mixture, nor give out heat, nor change the 
properties of the ingredients ,: its effect may 
be called solution or dissolution ; for instance, 
when oxygen gas and azotic gas are mixed in 
due proportion, they constitute atmospheric air, 
in which they retain their distinguishing pro- 

It is upon this supposed solution of one 
elastic fluid in another that I intend to make a 
few observations. That I have not misre- 
presented the author's ideas, will, I think, ap- 
pear from the following quotations. " When 
different gases are mixed, whose action is con- 
fined to this solution, no change is observed in 
the temperature, or in the volume resulting from 
the mixture ; hence it may be concluded, that 
this mutual action of two gases does not pro- 
duce any condensation, and that it cannot sur- 
mount the effort of the elasticity, or the af- 
finity for caloric, so that the properties of each 
gas are not sensibly changed — ." " Although 
both the solution and combination of two 
gases are the effect of a chemical action, which 
only differs in its intensity, a real diflference 
may be established between them, because 
there is a very material difference between the 
results : the combination of two gases always 
leads to a condensation of their volume, and 


gives rise to new properties ; on their solution, 
the gases share in common the changes arising 
from compression and temperature, and pre- 
serve their individual properties, which are 
only diminished in the ratio of the slight 
action which holds them united." (Page 198.) 
"The mutual affinity of the gases can, therefore, 
produce between them an effect which is 
greater than their difference of specific gravity, 
but which is inferior to the elastic tension 
which belongs to each molecule of both, so 
that the volume is not changed by this action ; 
the liquids which take the elastic state, com- 
port themselves afterwards like the gases." 
(Page 218.) "Solution must be distinguished 
from combination, not only because in the 
first, each of the substances is retained by an 
affinity so weak, that it preserves its dimen- 
sions. — " (Page 219.) Again, *' It cannot be 
doubted, that the parts of elastic fluids are not 
endued with the force of cohesion, as the sub- 
stances dissolved by them undergo an equal 
distribution, which could not happen but by 
the means of a reciprocal chemical attraction ; 
that which constitutes the force of cohesion." 
(Researches into the Laws of chemical affinity, 
Eng. Trans, page 57.) Here the translator 
has, I apprehend, mistaken the English idiom. 
The author means to say, that the parts of 


clastic fluids are endued with the force of 
cohesion ; but this he applies only to hetero- 
geneous particles. He certainly does not 
mean that the particles of homogeneous elastic 
fluids possess the force of cohesion. 

Newton has demonstrated from the phe- 
nomena of condensation and rarefaction that 
elastic fluids are constituted of particles, which 
repel one another by forces which increase in 
proportion as the distance of their centres 
diminishes: in other words, the forces are 
reciprocally as the distances. This deduction 
will stand as long as the Laws of elastic fluids 
continue to be what they are. What a pity it 
is that all who attempt to reason, or to theorise 
respecting the constitution of elastic fluids, 
should not make themselves thoroughly ac- 
quainted with this immutable Law, and con^ 
stantly hold it in their view whenever they 
start any new project ! When we contemplate 
a mixture of oxygenous and hydrogenous gas, 
v/hatdoes BerthoUet conceive, are the particles 
that repel each other according to the New- 
tonian Law ? The mixture must consist of 
such y and he ought in the very first instance 
to have informed us what constitutes the 
unity of a particle in his solution. If he 
grants that each particle of oxygen retains its 
unity, and each particle of hydrogen does the 


same, then we must conclude that the mutual 
action of two particles of oxygen is the same 
as that of a particle of oxygen, and one of 
hydrogen, namely, a repulsion according to 
the Law above stated, which effectually de- 
stroys the supposed solution by chemical 
agency. But if it be supposed that each par- 
ticle of hydrogen attaches itself to a particle of 
oxygen, and the two particles so united form 
one, from which the repulsive energy emanates; 
then the new elastic fluid may perfectly con- 
form to the Newtonian Law ; in this case a 
true saturation will take place when the num- 
ber of particles of hydrogen and oxygen in a 
mixture happen to be equal, or at least in the 
ratio of some simple numbers, such as 1 to 2, 
1 to 3, &c. Now something like this does 
actually take place when a real combination 
is formed, as for instance, steam, and nitric 
acid formed of a mixture of oxygen and 
nitrous gas. Here we have new elastic fluids, 
the atoms of which repel one another by the 
common Law, heat is given out, a great con- 
densation of volume ensues, and the new 
fluids differ from their constituents in their 
chemical relations. It remains then to deter- 
mine whether, in the instance of solution, all 
these effects take place in a ** slight" degree ; 
that is, in so small a degree as not to be 


cognisable to any of the senses. It certainly 
requires an extraordinary stretch of the. imagi- 
nation to admit the affirmative. 

One great reason for the adoption of this, 
or any other theory on the subject, arises fron> 
the phenomena of the evaporation of water. 
How is water taken up and retained in the 
atmosphere ? It cannot be in the state of 
vapour, it is said, because the pressure is too 
great : there must therefore be a true chemical 
solution. But when we consider that the sur- 
face of water is subject to a pressure equal to 
30 inches of mercury, and besides this pressure, 
there is a sensible affinity between the particles 
of water themselves ; how does the hisensible 
affinity of the atmosphere for water overcome 
both these powers ? It is to me quite inexpli- 
cable upon this hypothesis, the leading object of 
which is to account for this very phenomenon. 
Further, if a particle of air has attached a 
particle of water to it, what reason can be 
assigned why a superior particle of air should 
rob an inferior one of its property, when 
each particle possesses the same power? If a 
portion of common salt be dissolved in water 
and a little muriatic acid added ; is there any 
reason to suppose the additional acid displaces 
that already combined with the soda, and that 
upon evaporation the salt is not obtained with 


the identical acid it previously had ? Or, if 
oxygen gas be confined by water, is there any 
reason to suppose that the hydrogen of the 
water is constantly giving its oxygen to the air 
and receiving an equal quantity from the 
same ? Perhaps it will be said in the case of 
air dissolving water, that it is not the affection 
of one particle for one, it is that of a mass of 
particles for another mass ; it is the united 
action of all the atoms in the atmosphere 
upon the water, which raises up a particle. 
But as all these energies are reciprocal, the 
water must have a like action on the air, and 
then an atmosphere over water would press 
downward by a force greater than its weight, 
which is contradicted by experience. 

When two measures of hydrogen and one 
of oxygen gas are mixed, and fired by the 
electric spark, the whole is converted into 
steam, and if the pressure be great, this 
steam becomes water. It is most probable 
then that there is the same number of particles 
in two measures of hydrogen as in one of 
oxygen. Suppose then three measures of 
hydrogen are mixed with one of oxygen, and 
this slight affinity operates as usual ; how is the 
union effected ? According to the principle 
of equal division, each atom of oxygen ought 
to have one atom and a half of hydrogen at- 


tached to it ; but this is impossible ; one half 
of the atoms of oxygen must then take two of 
hydrogen, and the other half, one each. But 
the former would be specifically lighter than 
the latter, and ought to be found at the top of 
the solution j nothing like this is however 
observed on any occasion. 

Much more might be advanced to shew the 
absurdity of this doctrine of the solution of one 
gas in another, and the insufficiency of it to 
explain any of the phenomena ; indeed I 
should not have dwelt so long upon it, had 
I not apprehended that respectable authority 
was likely to give it credit, more than any ar- 
guments in its behalf derived from physical 

Dr. Thomson, in the 3d Edition of his 
System of Chemistry, has entered into a dis- 
cussion on the subject of mixed gases j he 
seems to comprehend the excellence and de- 
fects of my notions on these subjects, with 
great acuteness. He does not conclude with 
Berthollet, that on my hypothesis, " there 
would not be any augmentation of volume 
when aqueous and ethereal vapour was com- 
bined with the air," which has been so com- 
mon an objection. There is however one 
objection which this gentleman urges, that 
shews he does not completely understand the 



mechanism of my hypothesis. At page 448, 
Vol. 3. he observes that from the principles of 
hydrostatics, " each particle of a fluid sustains 
the whole pressure. Nor can I perceive any 
reason why this principle should not hold, 
even on the supposition that Dalton's hypo- 
thesis is well founded." Upon this I would 
observe, that when once an equilibrium is 
established in any mixture of gases, each par- 
ticle of gas is pressed as if by the surrounding 
particles of its oivn kind only. It is in the re- 
nunciation of that hydrostatical principle that 
the leading feature of the theory consists. The 
lowest particle of oxygen in the atmosphere 
sustains the weight of all the particles of 
oxygen above it, and the weight of no other. 
It was therefore a maxim with me, that every 
particle of gas is equally pressed in every di- 
rection, but the pressure arises from the particles 
of its own kind only. Indeed when a mea- 
sure of oxygen is put to a measure of azote, at 
the moment the two surfaces come in contact, 
the particles of each gas press against those of 
the other with their full force; but the two 
gases get gradually intermingled, and the force 
which each particle has to sustain proportionally 
diminishes, till at last it becomes the same as 
that of the original gas dilated to twice its 
volume. The ratio of the forces is as the cube 


root of the spaces inversely j that is, a* 
* V2 : 1, or as 1.26 : 1 nearly. In such a 
mixture as has just been mentioned, then, 
the common hypothesis supposes the pressure 
of each particle of gas to be 1.26; whereas 
mine supposes it only to be 1 ; but the sum 
of the pressure of both gases on the containing 
Tessel, or any other surface, is exactly the same 
on both hypotheses. 

Excepting the above objection, all the rest 
which Dr. Thomson has made, are of a nature 
not so easily to be obviated ; — he takes notice 
of the considerable time which elapses before 
two gases are completely diffused through each 
other, as Berthollet has done, and conceives 
this fact, makes against the supposition, that 
one gas is as a vacuum to another. He further 
objects, that if the particles of different gases 
are inelastic to each other ; then a particle of 
oxygen coming into actual contact with one of 
hydrogen, ought to unite with it, and form a 
particle of water ; but, on the other hand, he 
properly observes, that the great facility with 
which such combinations are effected in such 
instances as a mixture of nitrous and oxygen 
gas, is an argument in favour of the hypo- 
thesis. — Dr. Thomson founds another objection 
upon the facility of certain combinations, when 
Qne of the ingredients is in a nascent form ; 


that is, just upon the point of assuming the 
elastic state ; this, he observes, *' seems in- 
compatible with the hypothesis, that gases are 
not mutually elastic," Upon the whole. Dr. 
Thomson inclines to the opinion of Berthollet, 
that gases have the property of dissolving each 
other ; and admits, " however problematical 
it may appear at first view, that the gases not 
only mutually repel each other, but likewise 
mutually attract," I have no doubt if he had 
taken due time to consider this conclusion, he 
would, with me, have pronounced it absurd : 
but of this again in the sequel. 

With regard to the objection, that one gas 
makes a more durable resistance to the entrance 
of another, than it ought to do on my hy- 
pothesis : This occurred to me in a very early 
period of my speculations ; I devised the train 
of reasoning which appeared to obviate the 
objection ; but it being necessarily of a ma- 
thematical nature, I did not wish to obtrude it 
upon the notice of chemical philosophers, but 
rather to wait till it was called for. — The 
resistance which any medium makes to the 
motion of a body, depends upon the surface of 
that body, and is greater as the surface h 
greater, all other circumstances being the 
same. A ball of lead 1 inch in diameter meets 
with a certain resistance in falling through the 


air ; but the same ball, being made into a 
thousand smaller ones of -1^,5. of an inch di- 
ameter, and falling with the same velocity, 
meets with 10 times the resistance it did 
before : because the force of gravity increases 
as the cube of the diameter of any particle, 
and the resistance only as the square of the 
diameter. Hence it appears, that in order to 
increase the resistance of particles moving in 
any medium, it is only necessary to divide 
them, and that the resistance will be a maxi- 
mum when the division is a maximum. We 
have only then to consider particles of lead 
falling through air by their own gravity, and 
we may have an idea of the resistance of one 
gas entering another, only the particles of lead 
must be conceived to be irifinitely small, if I 
may be allowed the expression. Here we 
shall find great resistance, and yet no one, I 
should suppose, will say, that the air and the 
lead are mutually elastic. 

The other two objections of Dr. Thomson, 
I shall wave the consideration of at present. 

Mr. Murray has lately edited a system of 
chemistry, in which he has given a very clear 
description of the phenomena of the atmo- 
sphere, and of other similar mixtures of elastic 
fluids. He has ably discussed the different 
theories that have been proposed on the subject. 


and given a perspicuous view of mine, which 
he thinks is ingenious, and calculated to ex- 
plain several of the phenQmei^a well, but upon 
the whole, not equally satisfactory with that 
which he adopts. He does not object to the 
mechanism of my hypothesis in regard to the 
independent elasticity of the several gases en- 
tering into any mixture, but argues that the 
phenomena do not require so extraordinary a 
postulatum ; and more particularly disapproves 
of the application of my theory to account for 

The principal feature in Mr. Murray's 
theory, and which he thinks distinguishes it 
from mine, is " that between mixed gases, 
which are capable, under any circumstances 
of combining, an attraction must always be 
exerted." It is unnecessary to recount the 
arguments on behalf of this conclusion, because 
it will not be controverted. Mr. Murray an- 
nounces his views of the constitution of the 
atmosphere, as follows : " Perhaps that che- 
mical attraction which subsists between the 
solid bases of these gases, but which, when they 
are merely mixed together, cannot, from the dis- 
tance at which their particles are placed by 
the repulsive power of caloric, bring them into 
intimate union, may still be so far exerted, as 
to prevent their separation : or, they may be 


retained in mixture by that force of adhesion, 
which, exerted at the surfaces of many bodies, 
retains them in contact with considerable 
force." He supports these notions at length 
by various observations, and repeats some of 
the observations of Berthollet, whose doctrine 
on this subject, as has been seen, is nearly the 

Before we animadvert on these principles, 
it mav be convenient to extend the first a little 
farther, and to adopt as a maxim, " that be-. 
tween the particles o^ pure gases, which arc 
capable under any circumstances of combining, 
an attraction must always be exerted." This, 
Mr. Murray cannot certainly object to, in the 
case of steam, a pure elastic fluid, the par- 
ticles of which are known in certain circum- 
stances to combine. Nor will it be said that 
steam and a permanent gris are different ; for 
he justly observes, " this disthiction (between 
gases and vapours) is merely relative, and 
arises from the dilTerence of temperature at 
which they are formed ; the state with regard 
to each, while they exist in it, is precisely the 
same." Is steam then constituted of particles 
in which the attraction is so far exerted as to 
prevent their separation? No: they exhibit 
no traces of attraction, more than the like 
number of particles of oxygen do, when in 


the gaseous form. What then is the con- 
elusion ? It is this : ?iotivithsta?iding it must be 
allowed, that all hodieSy at all times, and in 
every situation, attract one aiiotlier ; yet in cer^ 
tain circumstances, they are likewise actuated 
ky a repulsive power ; the only efficient motive 
force is then the diffierence of these two 

From the circumstance of gases mixing to- 
gether without experiencing any sensible 
diminution of volume, the advocates for the 
agency of chemical affinity, characterise it as 
a " slight action," and " a weak reciprocal 
action :" So far I think they are consistent ; 
but when we hear of this affinity being so far 
exerted as to prevent the separation of elastic 
particles, I do not conceive with what pro- 
priety t can be called weak. Suppose this 
affinity should be exercised in the case of 
steam of 212°; then tlie attraction becoming 
equal to the repulsion, the force which any 
one particle would exercise must be equal to 
the weight of a column of water of 4896 feet 
high. (See page 146.) 

It is somewhat remarkable that those gases 
which are known to combine occasionally, as 
azote and oxygen, and those which are never 
known to combine, as hydrogen and carbonic 
acid, should dissolve one another with equal 


facility ; nay, these last exercise this solvent 
power with more effect than the former ; for, 
hydrogen can draw up carbonic acid from the 
bottom to tlie top of any vessel, notwithstand- 
ing the latter is 20 times the specific gravity of 
the former. One would have thought that a 
force of adhesion was more to be expected in 
the particles of steam, than in a mixture of 
hydrogen and carbonic acid. But it is the 
business of those who adopt the theory of the 
mutual solution of gases to explain these 

In a mixture where are 8 particles of oxygen 
for 1 of hydrogen, it is demonstrable that the 
central distances of the particles of hydrogen 
are at a medium twice as great as those of 
oxygen. Now supposing the central distance 
of two adjacent particles of hydrogen to be 
denoted by 12, query, what is supposed to 
be the central distance of any one particle of 
hydrogen from that one particle, or those 
particles of oxygen with which it is connected 
by this weak chemical union ? It would be 
well if those who understand and maintain 
the doctrine of chemical solution would re- 
present how they conceive this to be ; it would 
enable those who are desirous to learn, to obtain 
a clear idea of the system, and those who are 
dissatisfied with it, to point out its defects with 



more precision. The greatest possible central 
distance would be 8 i in the above instance, 
and the least might perhaps be 1. Berthollet, 
who decries the diagram by which I endea- 
voured to illustrate my ideas on this subject, 
has not given us any precise information, 
either verbally or otherwise, relative to the 
collocation of the heterogeneous particles, un- 
less it is to be gathered from the consideration 
that the affinity is so weak that the mixture of 
fluids preserves its dimensions. What can this 
weak affinity do, when opposed by a repulsive 
power of infinite superiority ? 

In discussing the doctrines of elastic fluids 
mixed with vapour, Mr. Murray seems dis- 
posed to question the accuracy of the fact, that 
the quantity of vapour is the same in vacuo as 
in air, though he has not attempted to ascertain 
in which case it more abounds. This is cer- 
tainly the touchstone of the mechanical and 
chemical theories ; and I had thought that 
whoever admitted the truth of the fact, must 
unavoidably adopt the mechanical theory. 
Berthollet however, convinced from his own 
experience, that the fact was incontrovertible, 
attempts to reconcile it, inimical as it is, to 
the chemical theory ; with what success it is 
left to others to judge. Mr. Murray joins 
with Berthollet in condemning as extravagant 


the position which I maintain, that if the at- 
mosphere were annihilated, we should have 
little more aqueous vapour than at present 
exists in it. Upon which I shall only remark, 
that if either of those gentlemen will calculate, 
or give a rough estimate upon their hypothesis, 
©f the quantity of aqueous vapour that would be 
collected around the earth, on the said supposi- 
tion, I will engage to discuss the subject with 
them more at large. 

In 1802, Dr. Henry announced ^ very 
curious and important discovery, which was 
afterwards published in the Philosophical Trans- 
actions ; namely, that the quantity of any gas 
absorbed by water is increased in direct pro- 
portion to the pressure of the gas on the sur- 
face of the water. Previously to this, 1 was 
engaged in an investigation of the quantity of 
carbonic acid in the atmosphere ; it was mat- 
ter of surprise to me that lime water should so 
readily manifest the presence of carbonic acid 
in the air, whilst pure water by exposure for 
any length of time, gave not the least traces 
of that acid. I thought that length of time 
ought to compensate for weakness of affinity* 
In pursuing the subject I found that the 
quantity of this acid taken up by water was 
greater or less in proportion to its greater or 
less density in the gaseous mixture, incumbent 


Upon the surface, and therefore ceased to b« 
surprised at water absorbing so insensible a 
portion from the atmosphere. I had not how- 
ever entertained any suspicion that this law- 
was generally applicable to the gases till Dr. 
Henry's discovery was announced. Immedi- 
ately upon this, it struck me as essentially ne- 
cessary in ascertaining the quantity of any gas 
which a given volume of water will absorb, 
that we must be careful the gas is perfectly 
pure or unmixed with any other gas whatever 5 
otherwise the maximum effect for any given 
pressure cannot be produced. This thought 
was suggested to Dr. Henry, and found to 
be correct ; in consequence of which, it be- 
came expedient to repeat some of his ex- 
periments relating to the quantity of gas 
absorbed under a given pressure. Upon due 
consideration of all these phenomena. Dr. 
Henry became convinced, that there was no 
system of elastic fluids which gave so simple, 
easy and intelligible a solution of them, as the 
one I adopt, namely, that each gas in any 
mixture exercises a distinct pressure, which 
continues the same if the other gases are with- 
drawn. In the 8th Vol. of Nicholson's Jour- 
nal, may be seen a letter addressed to me, in 
which Dr. Henry has clearly pointed out his 
reasons for giving my theory a preference. 


In the 9th Vol. is a letter from Mr. Gough, 
containing some animadversions, which vvere 
followed by an appropriate reply from Dr. 

In the 8th, 9th, and 10th Volumes of Ni- 
cholson's Journal, and in the first Vol. of the 
Manchester Memoirs fnezv series) may be 
seen some animadversions of Mr. Gough, on 
my doctrine of mixed gases, with some of 
his own opinions on the same subject. Mr. 
Gough conceives the atmosphere to be a 
chemical compound of gases, vapour, &c. and 
he rests his belief chiefly upon the observance 
of certain hygrometrical phenomena, such as 
that air absorbs moisture from bodies in certain 
cases, and in others restores it to them, shew- 
ing that air has an affinity for water, which may 
be overcome by another more powerful one. 
This opinion, as Mr. Murray observes, is the 
one we have from Dr. Halley ; it was supported 
by Le Roy, Hamilton and Franklin, and 
might be considered as the prevailing opinion, 
till Saussure, in his celebrated Essays on hy- 
grometry, published in 1783, suggested that 
water was first changed into vapour, and was in 
that state dissolved by the air. This amphibious 
theory of Saussure does not seem to have gained 
any converts to it, though it pointed out the 
instability of the other. Finally, the theory 


of the chemical solution of water in air, re- 
ceived its death blow in 1791, by the publica- 
tion of Pictet's Essay on Fire, and more par- 
ticularly by De Luc's paper on evaporation, 
published in the Philosophical Transactions 
for 1792. These gentlemen demonstrated, 
that all the train of hygrometrical phenomena 
takes place just as well, indeed rather quicker, 
in a vacuum, than in air, provided the same 
quantity of moisture is present. AH the 
influence that any kind or density of air has, 
is to retard the effect ; but in the end it be- 
comes the same. 

The only objection which Mr. Gough has 
presented that appears to me to raise any dif- 
ficulty, is that in regard to the propagation of 
sound : If the atmosphere consist chiefly of 
two distinct elastic media, it is urged that 
distant sounds ought to be heard double ; that 
is, the same sound would be heard twice, ac- 
cording as it was brought by one or other of 
the atmospheres. By calculation I find that 
if sound move at the rate of 1000 feet per 
second in an atmosphere of azotic gas, it 
ought to move in the other gases as follows : 



Sound moves in azotic gas 1000 per second. 
■ oxygen gas 930 ■■ 

— carb. acid 804 

— aqueous vap. 1175 

According to this table, if a strong and 
loud sound were produced 13 miles off, the 
first would be a weak impression of it brought 
by the atmosphere of aqueous vapour, in 99 
seconds ; the second would be the strongest 
of all, brought by the atmosphere of azotic 
gass, in 684- seconds; the third would be 
much inferior to the second, brought by the 
oxygenous atmosphere, in 74 seconds; the 
fourth and last brought by the carbonic acid 
atmosphere would be extremely weak, in 85 
seconds. — Now though observation does not 
perfectly accord with the theory in this re- 
spect, it comes as near it, perhaps, as it does 
to that of the more simple constitution of the 
atmosphere which Mr. Gough maintains. 
Derham, who has perhaps made the greatest 
number of accurate observations on distant 
sounds, remarked that the report of a cannon 
fired at the distance of 13 miles from him, did 
not strike his ear with a single sound, but that 
it was repeated 5 or 6 times close to each other. 
" The two first cracks were louder than the 


third ; but the last cracks were lounder than 
any of the rest." Cavallo, in his experimental 
philosophy, after quoting the above observa- 
tions, proceeds, " this repetition of the sound 
probably originated from the reflection of a 
single sound, from hills, houses, or other objects, 
not much distant from the cannon. But it 
appears from general observation, and where 
no echo can be suspected, that the sound of a 
cannon, at the distance of 10 or 20 miles, is 
different from the sound when near. In the 
latter case, the crack is loud and instantaneous, 
of which we cannot appreciate the height. 
Whereas in the former case, viz. at a distance, 
it is a grave sound, which may be compared to 
a determinate musical sound ; and instead of 
being instantaneous, it begins softly, swells 
to its greatest loudness, and then dies away 
growling. — Nearly the same thing may be 
observed with respect to a clap of thunder, 
other sounds are likewise altered in quality by 
the distance." (Vol. 2. page 331.) 

I shall now proceed to give my present 
views on the subject of mixed gases, which 
are somewhat different from what they were 
when the theory was announced, in conse- 
quence of the fresh lights which succeeding 
experience has diffused. In prosecuting my 
enquiries into the nature of elastic fluids, I 


soon perceived it was necessary, if possible, to 
ascertain whether the atoms or ultimate par- 
ticles of the different gases are of the same 
size or volume in like circumstances of tem- 
perature and pressure. By the size or volume 
of an ultimate particle, I mean in this place, 
the space it occupies in the state of a pure 
elastic fluid ; in this sense the bulk of the par- 
ticle signifies the bulk of the supposed im- 
penetrable nucleus, together with that of its 
surrounding repulsive atmosphere of heat. 
At the time I formed the theory of mixed 
gases, I had a confused idea, as many have, 
I suppose, at this time, that the particles of 
elastic fluids are all of the same size j that a 
given volume of oxygenous gas contains 
just as many particles as the same volume 
of hydrogenous ; or if not, that we had 
no data from which the question could 
be solved. But from a train of reason- 
ing, similar to that exhibited at page 71, I 
became convinced that different gases have 
not their particles of the same size : and that 
the following may be adopted as a maxim, 
till some reason appears to the contrary : 
namely, — 

That every species of pure elastic fuid has 
its particles globular and all of a size ; but 
that no two species agree in the size of their 


particles i the pressure and temperature being 
the same. 

There was another thing: concerning^ which 
I was dubious ; whether heat was the cause of 
repulsion. I was rather inclined to ascribe re- 
pulsion to a force resembling magnetism, 
which acts on one kind of matter, and has no 
effect on another. For, if heat were the cause 
of repulsion, there seemed no reason why a 
particle of oxygen should not repel one of 
hydrogen with the same force as one of its 
own kind, especially if they were botli of a 
size. Upon more mature consideration, I sec 
no sufficient reason for discarding the common 
opinion, which ascribes repulsion to heat ; 
and I think the phenomena of mixed gases 
may still be accounted for, by repulsion, 
without the postulatum, that their particles 
are mutually inelastic, and free from such of 
the preceding objections as I have left un- 

When we contemplate upon the disposition 
of the globular particles in a volume of pure 
elastic fluid, we perceive it must be analogous 
to that of a square pile of shot ; the particles 
must be disposed into horizontal strata, each 
four particles forming a square : in a superior 
stratum, each particle rests upon four particles 
below, the points of its contact with all four 


being 45° above the horizontal plane, or that 
plane which passes through the centres of 
the four particles. On this account the pres- 
sure is steady and uniform throughout. But 
when a measure of one gas is presented to a 
measure of another in any vessel, we have 
then a surface of elastic globular particles of 
one size in contact with an equal surface 
of particles of another : in such case the 
points of contact of the heterogeneous par- 
ticles must vary all the way from 40° to 
90°; an intestine motion must arise from 
this inequality, and the particles of one 
kind be propelled amongst those of the 
other. The same cause which prevented the 
two elastic surfaces from maintaining an equi- 
librium, will always subsist, the narticles of 
one kind being from their size unable to apply 
properly to the other, so that no equilibrium 
can ever take place amongst the heterogeneous 
particles. The intestine motion must therefore 
continue till the particles arrive at the opposite 
surface of the vessel against any point of which 
they can rest with stability, and the equilibrium 
at length is acquired when each gas is uni- 
formly diffused through the other. In the 
open atmosphere no equilibrium can take place 
in such case till the particles have ascended so 
far as to be restrained by their own weight ; 


that is, till they constitute a distinct atmo- 

It is remarkable that when two equal 
measures of different gases are thus diffused, 
and sustain an invaried pressure, as that of the 
atmosphere, the pressure upon each particle 
after the mixture is less than before. This 
points out the active principle of diffusion ; for, 
particles of fluids are always disposed to move 
to that situation where the pressure is least. 
Thus, in a mixture of equal measures of oxygen 
and hydrogen, the common pressure on each 
particle before mixture being denoted by 1, 
that after the mixture when the gas becomes 
of half its density, will be denoted by 
V4-= .794. 

This view of the constitution of mixed gases 
agrees with that which I have given before, in 
the two following particulars, which 1 con- 
sider as essential to every theory on the subject 
to give it plausibility. 

1st. The diffusion of gases through each 
other is effected by means of the repulsion 
belonging to the homogenous particles ; or to 
that principle which is always energetic to 
produce the dilatation of the gas. 

2d. When any two or more mixed gases 
acquire an equilibrium, the elastic energy of 
each against the surface of the vessel or of any 


liquid, is precisely the same as if it were the 
only gas present occupyinjj the whole space, 
and all the rest were withdrawn. 

In other respects I think the last view ac- 
cords better with the phenomena, and obviates 
the objections which Dr. Thomson has brought 
against the former; particularly in regard to 
the query, why mixed gases that are known on 
certain occasions to combine, do not always 
combine ; and why any gaseous particle in its 
nascent state is more disposed to combination 
than when it has already assumed the elastic 
form. It v^ill also more clearly explain the 
reason of one gas making so powerful and 
durable a resistance to the entrance of another. 

One difficulty still remains respecting va- 
pour, which neither view of the subject al- 
together removes : though vapour may subsist 
in the atmosphere upon either supposition, as 
far as the temperature will admit, not being 
subject to any more pressure than would arise 
from its own particles, were the others re- 
moved, yet it may be enquired, how does it 
rise from the surface of water subject to the 
pressure of the atmosphere? how does vapour 
which ascends with an elastic force of only 
half an inch of mercury, detach itself from 
water when it has the weight of 30 inches of 
mercury to oppose its ascent ? This difficulty 


applys nearly the same to all theories of the 
solution of water in air, and it is therefore 
of consequence for every one, let him adopt 
what opinion he may, to remove it. Chemical 
solution but ill explains it ; for, the affinity of 
air for vapour is always described as weak, 
and yet it is sufficient to overcome the pressure 
of a powerful force equal to the weight of the 
atmosphere. I have endeavoured to shew in 
another place (Manch. Memoirs, Vol. 1. new 
series, page 284) what my own ideas on the 
subject are. It appears to me, that it is not till 
the depth of 10 or 12 strata of particles of 
any liquid, that the pressure upon each per- 
pendicular column becomes uniform ; and 
that several of the particles in the uppermost 
stratum are in reality subject to but little 

I9i on LIQUIDS. 



And the Mechanical Relations betwixt Liquids 
and Elastic Fluids. 

A liquid or inelastic fluid may be defined 
to be a body, the parts of which yield to a 
very small impression, and are easily moved 
one upon another. This definition may suffice 
for the consideration of liquids in an hy- 
drostatical sense, but not in a chemical sense. 
Strictly speaking, there is no substance in- 
elastic; if heat be the cause of elasticity, all 
bodies containing it must necessarily be elastic: 
but we commonly apply the word elastic to 
such fluids only as have the property of con- 
densation in a very conspicuous degree. 
Water is a liquid or inelastic fluid ; but if it 
is compressed by a great force, it yields a little, 
and again recovers its original bulk when the 
pressure is removed. We are indebted to 
Mr. Canton for a set of experiments by which 
the compressibility of several liquids is de- 
monstrated. Water, he found, lost about 


^^l-^th part of its bulk by the pressure of 
the atmosphere. 

When we consider the origin of water from 
steam, we have no reason to wonder at its 
compressibility, and that in a very small de- 
gree J it would be wonderful if water had not 
this quality. The force of steam at 212° is 
equal to the pressure of the atmosphere ; 
what a prodigious force must it have when 
condensed 15 or 18 hundred times? We 
know that the particles of steam, reduced to 
the state of water, still retain the greatest part 
of their heat. What a powerful resistance then 
ought they not to make against a compressing 
force ? The truth is, water, and by analogy, 
other liquids, must be considered as bodies, 
under the controul of two most powerful and 
energetic agents, attraction and repulsion, 
between which there is an equilibrium. If 
any compressing force is applied, it yield?, 
indeed, but in such a manner, as a strong 
spring would yield, when wound up almost 
to the highest pitch. When we attempt to 
separate one portion of liquid from another, 
the case is different : here the attraction is the 
antagonist force, and that being balanced by 
the repulsion of the heat, a moderate force is 
capable of producing the separation. But 


even here we perceive the attractive force to 
prevail, there being a manifest cohesion of the 
particles. Whence does this arise ? It should 
seem that when two particles of steam coalesce 
to form water, they take their station so as to 
effect a perfect equilibrium between the two 
opposite powers ; but if any foreign force in- 
tervene, so as to separate the two molecules 
an evanescent space, the repulsion decreases 
faster than the attraction, and consequently 
this last acquires a superiority or excess, which 
the foreign force has to overcome. If this 
were not the case, why do they at first, or 
upon the formation of water, pass from the 
greater to the less distance ? 

With regard to the collocation and arrange- 
ment of particles in an aggregate of water or 
any other liquid, I have already observed 
(page 139) that this is not, in all probability, 
the same as in air. It seems highly improbable 
from the phenomena of the expansion of 
liquids by hear. The law of expansion is 
unaccountable for, if we confine liquids to 
one and the same arrangement of their ultimate 
particles in all temperatures ; for, we cannot 
avoid concluding, if that were the case, 
the expansion would go on in a progressive 
way with the heat, like as in air y and there 


would be no such thing observed as a point 
of temperature at which the expansion was 


Reciprocal Pressure of Liquids and Elastic 


When an elastic fluid is confined by a vessel 
of certain materials, such as wood, earthen- 
ware, &c. it is found slowly to communicate 
with the external air, to give and receive suc- 
cessively, till a complete intermixture takes 
place. There is no doubt but this is oc- 
casioned by those vessels being porous, so as 
to transmit the fluids. Other vessels, as those 
of metal, glass, &c. confine air most com- 
pletely. These therefore cannot be porous ; 
or rather, their pores are too small to admit of 
the passage of air. I believe no sort of vessel 
has yet been found to transmit one gas and 
confine another; such a one is a desideratum 
in practical chemistry. All the gases appear 
to be completely porous, as might be expected, 
and therefore operate very temporarily in con- 
fining each other. How are liquids in this 
respect ? Do they resemble glass, or earthen- 


ware, or gases, in regard to their power of 
confining clastic fluids ? Do they treat all 
gases alike, or do they confine some, and 
transmit others ? These are important questions: 
they are not to be answered in a moment. 
We must patiently examine the facts. 

Before we can proceed, it will be necessary 
to lay down a rule, if possible, by which to 
distinguish the chemical from the mechanical 
action of a liquid upon an elastic fluid. I 
think the following cannot well be objected 
to : When an elastic Jiuid is kept in contact 
ivith a liquidf if any change is perceived, either 
in the elasticity or any other property of the 
elastic Jluid, so far the mutual action must be 
pronounced chemical : but if no change is 
perceived, either in the elasticity or any other 
property of the elastic fluid, then the mutual 
action of the tzvo must be pronouiKed wholly 


If a quantity of lime be kept in water and 
agitated, upon standing a sufficient time, the 
lime falls down, and leaves the v/ater trans- 
parent : but the water takes a small portion of 
of the lime which it permanently retains, con- 
trary to the Laws of specific gravity. Why } 
Because that portion of iime is dissolved by 
the water. If a quantity of air be put to water 


and agitated, upon standing a sufficient time, 
the air rises up to the surface of the water and 
leaves it transparent; but the water permanently 
retains a portion of air, contrary to the Laws 
of specific gravity. Why ? Because that small 
portion of air is dissolved by the water. So 
far the two explanations are equally satisfactory. 
But if we place the two portions of water 
under the receiver of an air pump, and exhaust 
the incumbent air, the whole portion of air 
absorbed by the water ascends, and is drawn 
out of the receiver ; whereas the lime remains 
still in solution as before. If now the question 
be repeated, why is the air retained in the 
water ? The answer must be, because there is 
an elastic force on the surface of the water 
which holds it in. The water appears passive 
in the business. But, perhaps, the pressure on 
the surface of the water may have some effect 
upon its affinity for air, and none on that for 
lime? Let the air be drawn off from the 
surfaces of the two portions of water, and 
another species induced without alleviating 
the pressure. The lime water remains un- 
changed ; the air escapes from the other much 
the same as in vacuo. The question of the 
relation of water to air appears by this fact to 
be still more difficult; at first the air seemed 


to be retained by the attraction of the water ; 
in the second case, the water seemed indiffer- 
ent ; in the third, it appears as if repulsive to 
the air ; yet in all three, it is the same air that 
has to act on the same water. From these 
facts, there seems reason then for maintaining 
three opinions on the subject of the muiual 
action of air and water ; namely, that water 
attracts air, that water does not attract it, and 
that water repels air. One of these must be 
true ; but we must not decide hastily. Dr. 
Priestley once imagined^ that the clay of a 
porous earthen retort, when red hot, " destroys 
for a time the aerial form of whatever air is 
exposed to the outside of it j which aerial 
form it recovers, after it has been transmitted 
in combination from one part of the clay to 
another, till it has reached the inside of the 
retort." But he soon discarded so extravagant 
an opinion. 

From the recent experiments of Dr. Henry, 
with those of my own, there appears reason 
to conclude, that a given volume of water 
absorbs the following parts of its bulk of the 
several gases. 


ulk of gas 


1 = 


1 - 


1 = 



I — 


a 7 = 



2 7 = 


2 7 


TT ~ 


Carbonic acid 

Sulphuretted hydrogen 

Nitrous oxide 

Olefiant gas 

Oxygenous gas 

Nitrous gas 

Carburetted hydrogen 

Carbonic oxide ? 

Azotic gas 

~ =; .0156 Hydrogenous gas 
~4- = .0156 Carbonic oxide ? 

These fractions are the cubes of 4, f, h i, &c. this 
shews the distances of the gaseous particles in the water to 
be always same multiple of the distances without. 

In a mixture of two or more gases, the rule 
holds the same as when the gases are alone ; 
that is, the quantity of each absorbed is the 
same as if it was the only gas present. 

As the quantity of any gas in a given volume 
is subject to variation from pressure and tem- 
perature, it is natural to enquire whether any 
change is induced in the absorption of these 


circumstances ; the experiments of Dr. Henry 
have decided this point, by ascertaining, that 
if the exterior gas is condensed or rarefied in 
any degree, the gas absorbed is condensed or 
rarefied in the same degree j so that the pro- 
portions absorbed given above are absolute. 

One remarkable fact, which has been hinted 
at is, that no one gas is capable of retaining 
another in vv'ater ; it escapes, not indeed in- 
stantly, like as in a vacuum, but gradually, like 
as carbonic acid escapes into the atmosphere 
from the bottom of a cavity communicating 
with it. 

It remains now to decide whether the re- 
lation between water and the abovementioned 
gases is of a chemical or mechanical nature. 
From the facts just stated, it appears evident 
that the elasticity of carbonic acid and the 
other two gases of the first class is not at all 
affected by the water. It remains exactly of 
the same energy whether the water is present or 
absent. All the other properties of those gases 
continue just the same, as far as I know, 
whether they are alone or blended with water; 
we must therefore, I conceive, if we abide by 
the Law just laid down, pronounce the mutual 
action between these gases and water to be 

A very curious and instructive phenomenon 


takes place when a portion of any of the 
above three gases is thrown up into an eu- 
diometer tube of -j-V of an inch diameter over 
water; the water ascends and absorbs the gas 
with considerable speed ; if a small portion of 
common air is suddenly thrown up, it ascends 
to the other, and is commonly separated by a 
fine film of water for a time. That instant the 
the two airs come into the above situation, the 
water suddenly ceases to ascend in the tube, 
but the film of water runs up with great speed, 
enlarging the space below, and proportionally 
diminishing that above, till it finally bursts. 
This seems to shew that the film is a kind of 
sieve through which those gases can easily pass, 
but not common air. 

In the other gases it is very remarkable their 
density within the water should be such as to 
require the distance of the particles to be just 
2, 3 or 4 times what it is without. In olefiant 
gas, the distance of ^he particles within is just 
twice that without, as is inferred from the 
density being ^. In oxygenous gas, &c. the 
distance is 3 times as great, and in hydro- 
genous, Szc. 4 times. This is certainly curious, 
and deserves further investigation ; but at pre- 
sent we liave only to decide whether the ge- 
neral phenomena denote the relation to be of a 
chemical or mechanical nature. In no case 


whatever does it appear that the elasticity of 
any of these gases is affected ; if water takes 
■^■j. of its bulk of any gas, the gas so absorbed, 
exerts ^V of the elasticity, that the exterior 
gas does, and of course it escapes from the 
water v\hen the pressure is withdrawn from 
its surface, or when a foreign one is induced, 
against which it is not a proper match. As 
far as is known too, all the other properties of 
the gases continue the same ; thus, if water 
containing oxygenous gas be admitted to 
nitrous gas, the union of the two gases is 
certain ; after which the water takes up -j^ 
of its bulk of nitrous gas, as it would have 
done, if this circumstance had not occurred. 
It seems clear then that the relation is a media- 
nical one.* 

* Dr. Thomson and Mr. Murray have both written 
largely in defence of the notion that all gases are combined 
with water, that a real union by means of a chemical 
affinity which water exercises in a greater or less degree 
towards all gases, takes place ; thjs affinity is supposed to 
be of the slight kind, or of that kind which holds all gases 
in a state of solution, one amongst another, without any 
distinction. The oppposite doctrine was fnst stated in a 
paper of mine, on the absorption of gases by water. 
(Mancli. Memoirs, new series, Vol. 1.) Previously to the 
publication of that paper, Dr. Henr}', who was convinced 
from his own experience, that the connection of gases 
with water was of a mechanical nature, wrote two essavs m 


Carbonic acid gas then presses upon water 
in the first instance with its whole force ; in 
a short time it parrly enters the water, and 
then the reaction of the part entered, contrl- 

the 8th ariH 9th Vol. of Nicholson's Journal, in vvhich the 
arguinenis lor tJnt opinion are clearly, an«J, I think, un- 
ansu\rnl)iy stat'^d. I do not intend to enter largely into a 
discission ot" the argiin'er.ts these gentlemen adopt. Dr. 
Thoriijo t'a If^ading argument seems lo be, that " water will 
absorb such a portion of each gn--, that the repuUion be- 
tween the pai tides absorbed, just balances the affinity of 
water for iheai.'^ H^: then proceeds to infer, that the 
afTinity of carbonic acid for water is such as nearly to 
balance the elasticity, that the affinity of okfiant gas for 
water is equal to half its elasticity, that of oxygen, ^, and 
of azote I, &c. Now if a particle of water attract one of 
carbonic acid by a force analogous to that of repulsion, it 
must increase directly as the distance decreases ; if so, two 
such particles must be in equilibrium at any distance ; and 
if any other force is applied to the particle of gas pro- 
pelling it towards the water, the two particles nnist unite 
or coiiie into most intimate contact. Hence, I should infer, 
froio Dr. Thomson's principle, that each particle of water 
would lake one of acid, and consequently lib. of water 
wouhl combine with 2|lbs. of carbonic acid nearly. Mr. 
Murray mentions a great many circumstances which he 
conceives make against the mec hanical hypothesis ; for 
instance, some of the acid and alkaline gases are known to 
be absorbed largely by water, and undoubtedly by affinity ; 
therefore the less absorbable gases must be under the same 
influence, only in an inferior degree, and that "it would 
be impossible to point out the line of distinction between 
those where the absorption might beconcLired to be purely 


butes to support the incumbent atmosphere. 
Finally, the gas gets completely diiTused 
through the water, so as to be of the same 
density within ag without ; the gas within the 
water then presses on the containing vessel 
only, and reacts upon the incumbent gas. 
The water then sustains no pressure either 
from the gas within or without- In olefiant 
gas the surface of the water supports ~l of 
the pressure, in oxygenous, &c. j^, and in 
hydrogenous, &c. -Ij-. 

When any gas is confined in a vessel over 

mechanical, and those where the exertion of affinity must 
be allowed to operate." I conceive nothing is more easy 
than to point out the exact line of distinction : wherever 
water is found to diminish or destroy the elasticity of any gas, 
it is a chemical agent ; wherever it does neither of these, it 
is a mechanical agent. Whoever undertakes to maintain 
the chemical thtory of the absorption of gases by water, 
should in the outset overturn the following argument pre- 
ferred by Dr. Henry : " The quantity of every gas, 
absorbed by water, follows exactly the ratio of the pres- 
sure ; and since it is a rule in philosophizing, that effects 
qf the same kind, though differing in degree, are pro- 
duced by the same cause, it is perfectly safe to conclude, 
that everj', even the minutest portion of any gas, in a 
state of absorption by water, is retained entirely by incum- 
bent pressure. Tliere is no occasion, therefore, to call in 
the aid of the law of chemical affinity, when a me- 
chanical law fully and satisfactorily explains the ap- 


water in the pneumatic trough, so as to com- 
municate with the atmosphere through the 
medium of water, that gas must constantly 
be filtring through the water into the atmo- 
sphere, whilst the atmospheric air is filtring 
through the water the contrary way, to sup- 
ply its place in the vessel j so that in due 
time the air in the vessel becomes atmospheric, 
as various chemists have experienced. Water 
in this respect is like an earthenware retort : 
it admits the gases to go both ways at the 
same time. 

It is not easy to assign a reason why water 
should be so permeable to carbonic acid, &c. 
and not to the other gases; and why there 
should be those differences observable in the 
others. The densities 4-> iV ^"^ -V> ^lave 
most evidently a reference to a mechanical 
origin, but none whatever to a chemical one. 
No mechanical equilibrium could take place 
if the densities of the gases within were not 
regulated by this law j but why the gases 
should not all agree in some one of these forms, 
I do not see any reason. 

Upon the whole it appears that water, like 
earthenware, is incapable of forming a per- 
fect barrier to any kind of air ; but it differs 
from earthenware in one respect ; the last is 
alike permeable to all the gases, but water is 


much more permeable to some gases than to 
others. Other liquids have not been sufBciently 
examined in this respect. 

The iv.utual action of water, and the greater 
number ot acid gases and alkaline gas partaking 
most evidently of a chemical nature, will be 
best considered under the headsof the respective 
acids and alkalis. 




A solid body is one, tlie particles of which 
arc in a state of equilibrium betAixt two 
great powers, at'.racllon and repulsion, but 
in suc!^. r. nianner, that no change can be 
made in their distances without considerable 
force. If an approximation of the particles 
is attempted by force, then the heat resists it ; 
if a separation, then the attraction resists it. 
The notion of Boscovich of alternating planes 
of attraction and repulsion seems unnecessary; 
except that upon forcibly breaking the co- 
hesion of any body, the newly exposed surface 
must receive such a modification in its atmo- 


sphere of heat, as may prevent the future junc- 
tion of the parts, without great force. 

The essential distinction between liquids 
and solids, perhaps consists in this, that heat 
changes the figure of arrangement of the ulti- 
mate particles of the former continually and 
gradually, whilst they retain their liquid form ; 
whereas in the latter, it is probable, that change 
of temperature does no more than change the 
size, and not the arrangement of the ultimate 

NoJtwithstanding the hardness of solid bodies, 
or the difficulty of moving the particles one 
amongst another, there are several that admit 
of such motion without fracture, by the appli- 
cation of proper force, especially if assisted by 
heat. The ductility and malleability of the 
metals, need only to be mentioned. It should 
seem the particles glide along each others sur- 
face, somewhat like a piece of polished iron at 
the end of a magnet, without being at all 
weakened in their cohesion. The absolute 
force of cohesion, which constitutes the strength 
of bodies, is an enquiry of great practical im- 
portance. It has been found by experiment, 
that wires of the several metals beneath, being 
each T-V of an inch in diameter, were just 
broken by the annexed weights. 


Tin .... 



360 > 


Sil>er 370 

I^on 450 

Gold 500 

A piece of good oak, an inch square and a 
yard 1 >ng, will just bear in the middle 3301bs. 
But such a piece of wood should not in prac- 
tice be trusted, for any length of time, with 
above 4- or :^ of that weight. Iron is about 
10 times as strong as oak, of the same di- 
inens ons. 

One would be apt to suppose that strength 
and hardness ought to be found propor- 
tionate to each other ; but this is not the case. 
Glass is harder than iron, yet the latter is much 
the stronger of the two. 

Crystallization ■ xhibits to us the effects of 
the natural arrangement of the ultimate par- 
ticles of various co npound bodies; but we 
are sea cely yet sulhcieiitly acquainted with 
chemical synihesis and analysis to understand 
the rationale of this process. The rhomboidal 
form may ari^e from the proper position of 
4, 6, 8 or 9 globular particles, the cubic form 
from 8 particles, the triangular form from 3, 


6 or 10 particles, the hexahedral prism from 

7 particles, &c. Perhaps, in due time, we 
mav be enabled to ascertain the number and. 
order of elementary particles, constituting any 
given compound element, and from that 
determine the figure which it will prefer on 
crystallization, and vicd versd ; but it seems 
premature to form any theory on this subject, 
till we have discovered from other principles 
the number and order of the primary elements 
which combine to form some of the compound 
elements of most frequent occurrence ; the 
method for which we shall endeavour to point 
out in the ensuing chapter. 




W HEN any body exists in the elastic state, 
its ultimate particles are separated from each 
other to a much greater distance than in any 
other state; each particle occupies the centre 
of a comparatively large sphere, and supports 


its dignity by keeping all the rest, which by 
their gravity, or otherwise are disposed to en- 
croach up it, at a respectful distance. When 
we attempt to conceive the number of particles 
in an atmosphere, it is somewhat like attempt- 
ing to conceive the number of stars in the 
universe ; we are confounded with the thought. 
But if we limit the subject, by taking a given 
volume of any gas, we seem persuaded that, 
let the divisions be ever so minute, the number 
of particles must be finite j just as in a given 
space of the universe, the number of stars and 
planets cannot be infinite. 

Chemical analysis and synthesis go no far- 
ther than to the separation of particles one 
from another, and to their reunion. No new 
creation or destruction of matter is within the 
reach of chemical agency. We might as well 
attempt to introduce a new planet into the 
solar system, or to annihilate one already in 
existence, as to create or destroy a particle of 
hydrogen. All the changes we can produce, 
consist in separating particles that are in a state 
of cohesion or combination, and joining those 
that were previously at a distance. 

In all chemical investigations, it has justly 
been considered an important object to ascer- 
tain the relative iveights of the simples which 


constitute a compound. But unfortunately the 
enquiry has terminated here ; whereas from 
the relative weights in the mass, the relative 
weights of the ultimate particles or atoms of 
the bodies might have been inferred, from 
which their number and weight in various 
other compounds would appear, in order to 
assist and to guide future investigations, and to 
correct their results. Now it is one great 
object of this work, to shew the importance 
and advantage of ascertaining the relative 
weights of the ultimate particles, both of simple 
and compound bodies, the nuiJiber of simple 
elementary particles ivhich constitute one com- 
pound particle, and the number of less compound 
particles ivhich enter into the formation of one 
more compound particle. 

If there are two bodies, A and B, which 
are disposed to combine, the following is the 
order in which the combinations may take 
place, beginning with the most simple : 

1 atom of A -|- 1 atom of B = I atom of C, binar\%' 

1 atom of A + 2 atoms of B = I atom of D, ttrnaiy. 

2 atomsof A-}- I atom ofB=^ I atom of E, itniaiy. 

I atom of A -}- 3 atoms of B = 1 atom o\ F, quateiuaiy. 

3 atomsof A -f- I atom of B = 1 atom of G, quaternary. 

&c. &c. 


The following general rules may be adopted 
as guides in all our investigations respecting 
chemical synthesis. 

1st. When only one combination of two 
bodies can be obtained, it must be presumed to 
be a binary one, unless some cause appear to 
the contrary. 

2d. When two combinations are observed, 
they must be presumed to be a binary and a 

3d. When three combinations are obtained, 
we may expect one to be a binary^ and the 
other two ternary. 

4th. When four combinations are observed, 
we should expect one binary y two ternary ^ and 
one quaternary, &c. 

5th. A binary compound should always be 
specifically heavier than the mere mixture of its 
two ingredients. 

6th. A ternary compound should be speci- 
fically heavier than the mixture of a binary 
and a simple, which would, if combined, 
constitute itj &c. 

7th. The above rules and observations 
equally apply, when two bodies, such as 
C and D, D and E, &c. are combined. 

From the application of these rules, to the 
chemical facts already well ascertained, we 


deduce the following conclusions; 1st. That 
water is a binary compound of hydrogen and 
oxygen, and the relative weights of the two 
elementary atoms are as 1 : 7, i;early ; 2d. That 
ammonia is a binary coinpound of hydrogen 
and azote, and the relative weights of the two 
atoms are as 1:5, nearly ; 3d. That nitrous 
gas is a binary compound of azote and oxygen, 
the atoms of which weigh 5 and 7 respec- 
tively ; that nitric acid is a binary or ternary 
compound according as it is derived, and con- 
sists of one atom of azote and two of oxygen, 
together weighing 19; that nitrous oxide is a 
compound similar to nitric acid, and consists 
of one atom of oxygen and two of azote, 
weighing 17; that nitrous acid is a binary 
compound of nitric acid and nitrous gas, 
weighing 31 ; that oxynitric acid is a binary 
compound of nitric acid and oxvgen, weighing 
26 ; 4th. That carbonic oxide is a binary com- 
pound, consisting of one atom of charcoal, and 
one of oxygen, together weighing nearly 12; 
that carbonic acid is a ternary compound, (but 
sometimes binary) consisting of one atom of 
charcoal, and two of oxygen, weighing 19; 
&c. &c. In all these cases the weights are 
expressed in atoms of hydrogen, each of which 
is denoted by unity. 


In the sequel, the facfs and experiments 
from which these conclusions are derived, will 
be detailed ; as well as a great variety of others 
from which are inferred the constitution and 
weight of the ultimate particles of the princi" 
pal acids, the alkalis, the earths, the metals, 
the metallic oxides and sulphurets, the long 
train of neutral salts, and in short, all the 
chemical compounds which have hitherto 
obtained a tolerably good analysis. Several 
of the conclusions will be supported by origi- 
nal experiments. 

From the novelty as well as importance of 
the ideas suggested in this chapter, it is deemed 
expedient to give plates, exhibiting the mode 
of combination in some of the more simple 
cases. A specimen of these accompanies this 
first part. The elements or atoms of such 
bodies as are conceived at present to be simple, 
are denoted by a small circle, with some dis- 
tinctive mark j and the combinations consist in 
the juxta-position of two or more of these ; 
when three or more particles of elastic fluids 
are combined together in one, it is to be sup- 
posed that the particles of the same kind repel 
e^ch other, and therefore take their stations 


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( 217 ) 


PLATE L Fig. 1. is intended to illustrate the au- 
thor's ideas on the subject of the capacities of bodies for 
heat. See page 3. There are three cylindrical vessels 
placed one within another, having no communication but 
over their margins ; the innermost is connected with a la« 
teral and parallel lube graduated, and supposed to repre- 
sent the degrees of a thermometer, the scale of which com- 
mences at absolute cold; if a liquid (supposed to represent 
heat) be poured into the tube, it will flow into the inner 
vessel, through an aperture at the bottom, and rise to the 
same level in the vessel and the tube. Equal increments 
of heat in this case are supposed to produce equal incre- 
ments of temperature. When the temperature has arrived 
at a certain point (suppose 6000°) the body may be sup- 
posed to change its solid form to the liquid, as from ice to 
water, in which case its capacity for heat is increased, and 
is to be represented by the second vessel. A considerable 
portion of liquid must then be poured into the tube before 
any rise will be perceived, because it flows over the mar- 
gin of the innermost vessel into the lateral cavity of the 
second; at length it reaches the level, and then a pro- 
portional rise will ensue, till the body becomes converted 
into an elastic fluid, when the thermometer again becomes 
stationary — whilst a great portion of heat is entering into 
the body, now assuming a new capacity. 

Fig. 2. is a comparative view of the old and new divisions 
of the scale of the mercurial thermometer. See Table, 
page 14. The interval from freezing to boiling: water is 
180** on both scales, and the extremes are numbered 32* 
and 212" respectively. There are no other points of tem- 
perature in which the two scales can agree. 

Fig. 3. is a view of the divisions of a water thermometer, 
conformably to the new scale of the mercurial ; the lowt-st 
point is at 4-5® ; the intervals from 45'* upwards, to 55*, 
65», 75**, &c. are as the numbers 1, 4, 9, &c. Also, 
SO* and 60"^ coincide, as do 20« and 70<>, &c. 

PLATE n. Fig. 1. represents an air thermometer, or 
the expansion of air by heat ; the numbers are Fahrenheit's, 
and the intervals are such as represented in the 7th column 
of the table, at page 14. 

Fig. 2. is the logarithmic curve, the ordinates of which 
are erected at equal intervals, and diminish progressively 
by the ratio f . The intervals of the absciss or base of the 


curve, represent equal intervals of temperature (25° for 
steam or aqu ous vapour, and 34" for ethereal vapour) 
the ordinales represent inches of mercury, the weight of 
which is equal to the force of steam at the t( mperature. 
See thf 8ih and 9lh rnlumns of table, at pagf 14. Thus the 
force of steam at 212°, and of ethereal vapour at llC, 
new scale, is equal to 30 inches of mercury ; at 187° the 
force of steam is half as much, or 15 inches, and at 76°, 
that of ethereal vapour is also 15 inches, &c. 

Fig. 3. is a device suggested by Mr. Ewart, to illustrate 
the idea which I have developed in the section on the tem- 
perature of the atmosphere. It is a cylindrical vessel cloj;e 
at one end and open at the other, having a moveable pis- 
ton sliding within it : the vessel is supposed to contain air, 
and a weight is connected with the piston as a counterpoise 
to it. There is also a thermometer supposed to pass 
through the side of the vessel, and to be cemented into it. 
Now if we may suppose the piston to move without 
friction, and the vessel to be taken up into the atmosphere, 
the piston will gradually ascend, and suffer the air within 
to dilate, so as to correspond every where with the exterior 
air in density. This dilatation tends to diminish the tem- 
perature of the air within (provided no heat is acquired 
from the vessel.) Surh an instrument would shew what 
the theory requires namely, that the temperature of the 
air within would every where in the same vertical column 
agree vvith that without, though the former would not re- 
ceive or part with any heat absolutely, or in any manner 
communicate with the external air. 

PLATE III. See page 135.— The balls in Fig. 1 and 2 
represent particles of water : in the former, the square 
form denotes the arrangement in water, the rhomboidal 
form in the latter, deiioit-s the arrangement in ice. The 
angle is always 60° or 120°. 

Fig. 3. represent* the perpendicular section of a ball 
resting upon two others, as 4 and 8, Fig. 1. 

Fig. 4. represents the perpendicular section of a ball 
resting upon two balls, as 7 and 5, Fig. 2. The perpen- 
diculars of the triangles shew the heights of the strata in 
the two arrangements. 

Fig. 5 represents one of the small spiculae of ice formed 
upon the sudden congelation of water cooled below the 
frerziog point. See page 134. 

Fig. 6. represents the shoots or ramihcations of ice at 
the com nencemeat of congelation. The angles are 60° 
and 120° 

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PLATE IV. This plate contains the arbitrary marks 
or signs chosen to represent the several chemical elements 
or ultimate particles. 

Fig. Fig. 

1 Hvdrog. its rel. weight 1|11 Strontites - - - 46 

2 Azote, 5.12 Barytes - - - - 68 

3 Carbone or,charcoal, - 5 13 Iron ----- 38 

4 Oxygen, - - - - 7 14 Zinc - . - . . 56 

5 Phosphorus, - - - 15 Copper • - - - 56 

6 Sulphur, - - - - 13 16 Lead 95 

7 Magnesia, - - - - 20 

8 Lirae, 23 

9 Soda, 28 

17 Silver 100 

18 Plaiina - - - - 100 

19 Gold 140 

10 Potash, - - - - 42 20 Mercury - - - - 167 

21. An atom of water or steam, composed of 1 of 

oxygen and 1 of hydrogen, retained in physical 
contact by a strong affinity, and supposed to 
be surrounded by a common atmosphere of 
heat ; its relative weight = ----- 8 

22. An atom of ammonia, composed of 1 of azote and 

1 of hydrogen ---------- 6 

23- An atom of nitrous gas, composed of 1 of azote 

and 1 of oxygen --------- 12 

24. An atom of defiant gas, composed of 1 of carbone 

and I of hydrogen --------- 6 

25 An atom of carbonic oxide composed of 1 of car- 
bone and 1 of oxygen -------- ]2 

26. An atom of nitrous oxide, 2 azote + 1 oxygen - 17 

27. An atom of nitric acid, 1 azote -f- 2 oxygen - - 19 

28. An atom of carbonic acid, 1 carbone -j- 2 oxygen 19 

29. An atom of carburelted hydrogen, 1 carbone -{- 2 

hydrogen ------------ 7 

30. An atom of oxv nitric acid, 1 azote -j- 3 oxygen 26 

31. An atom of sulphuric acid, 1 sulphur -f- 3 oxygen 34 

32. An atom of sulphuretted hydrogen, 1 sulphur -|- 3 

hydrogen ----------- ig 

33. An atom of alcohol, 3 carbone -f- 1 hydrogen - 16 

34. An atom of nitrous acid, 1 nitric acid -f- 1 nitrous 

gas -31 

35. An atom of acetous acid, 2 carbone -f- 2 water - 26 

36. An atom of nitrate of ammonia, 1 nitric acid -j- 1 

ammonia + 1 water ------.-33 

37. An atom of sugar, 1 alcohol -\- 1 carbonic acid - 35 


Enough has been given to shew the method ; it will be 
quite unnecessary to devise characters and combinations of 
them to exhibit to view in this way all the subjects that 
come under investigation ; nor is it necessary to insist upon 
the accuracy of all these compounds, both in number and 
weight ; the principle will be entered into more particularly 
bereafter, as far as respects the individual results. It is not 
to be understood that all those articles marked as simple 
substances, are necessarily such by the theory ; they are 
only necessarily of such weights. Soda and Potash, such 
as they are found in combination with acids, are 28 and 42 
respectively in weight ; hut according to Mr. Davy's very 
important discoveries, thev are metallic oxides; the former 
then must be considered as composed of an atom of metal, 
21, and one of oxygen, 7 ; and the latter, of an atom of 
metal, 35, and one of oxygen, 7. Or, soda contains 75 
per cent, metal and 25 oxygen ; potash, 83.3 metal and 
16.7 oxygen. It is particularly remarkable, that accord- 
ing to the above-mentioned gentleman's essay on the De- 
composition and Composition of the fixed alkalies, in the 
Philosophical Transactions (a copy of which essay be has 
just favoured me with) it appears that " the largest quan- 
tity of oxygen indicated by these experiments was, for 
potash 17, and for soda, 20 parts in 100, and the smallest 
13 and 19/' 


Plate I to face page 217. 

2 to face page 218. 

3 to follow plate 2. 

4 to face page 219. 









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Reprodlced in Facsimile 

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HUMPHRY DAVY, Esq. Sec. R. S. 

















HEN the first part of this work was published, 1 ex- 
pected to complete it in little more than a year ; now two 
years aiiJ a half have elapsed, and it is yet in a state of im- 
perfection. The reason of it is, the great range of experi- 
ments which I have found necessary to take. Having been 
in my progress so often misled, by taking for granted the 
results of others, I have determined to write as little as pos- 
sible but. what I can attest by my own experience. On this 
account, the following work will b(^ found to contain more 
original facts and experiments, than any other of its size, 
on the elementary principles of chemistry. I do not mean 
to say that 1 have coj)ied the minutes olmy note-book ; iliis 
■would be almost as reprehensible as writing without any 
experience ; those who are conversant in practical che- 
mistry, know that not more than one new experiment in 
five is fit to be reported to the public ; the rest are found, 
upon due rcilection, to be some way or other defective, 
and are useful only as they shew the sources of error, and 
the means of avoiding it. 

Finding that my design could not be completed, without 
a second volume, I was desirous to finish the 5lb chapter, 
which treats of the compounds of two element?, in the part 
now edited ; but the work is enlarged ."^o much, and the 
time is so far advanced, that I have been obliged to omit 
two or three important sections, particularly the metallic 
oxides and sulphurets, which I am aware will demand no 
inconsiderable share of attention. After these are disposed 
of, the 6th chapter will treat of compounds of 3 or more 
elements; this will comprehend the vegetable and other 
acids not yet noticed, the hydrosulphureis, the neutral salts, 
compound combustibles, &c. &c. 

Whatever may be the result of my plan to render the 
work somewhat like complete, by the addition of another 
volume, I feel great present satisfaction in having been 
enabled thus far to devclope that theory of chemical syn- 


thesis, \vhich> the longer I contemplate, the moie I am 
convinced of its irulh. Enough is already done to enable 
any one to form a judgment of it. The facts and observa- 
tions yet in reserve, are only of the same kind as those al- 
ready advanced ; if the latter are not sufficient to convince, 
the addition of the former will be but of little avail. Iti 
the mean time, those who, with nje, adopt the system, 
will, I have no doubt, find it a very useful guide in the 
prosecution of all chemical investigations. 

In the arrangement of the articles treated of, I have enr 
deavoured to preserve order ; namely, to take such bodies 
as are simple, according to our present knowledge ; and 
next, those bodies that are compounds of two elements ; 
but in this I have not always succeeded. For, in some in- 
stances, it has not been quite clear what was simple, and 
what compound ; in others, the compounds of three or more 
elements have been so intimately connected with those of 
two, that it was found impracticable to give a satisfactory 
account of the latter, without entering more or less into a 
description of the former. 

In regard to nomenclature, I have generally adopted 
what was most current ; perhaps, in a few instances, my 
peculiar views may have led me to deviate from this rule. 
1 have called those salts carbonates, which are constituted 
of one atom of carbonic acid united to one of base; and the 
like for other salts. But some moderns call the neutral salts 
carbonates, and the former subcarbonalcs ; whereas, I should 
call the neutral carbonates of soda and potash supercar- 
honatcs, consisting of two atoms of acid and one of base. I 
have, however, continued to call the common nitrates by 
that name, though most of them must be considered on my 
system as svpeniitrates. I am not very anxious upon this 
head, as it is evident that if the system I proceed upon bo 
adopted, a general reformation of nomenclature will be the 
consequence, having a reference to the n?<wiifr o/'ft/o//(j, as 
well as to the kind of elements, consliluling the difTerent 
compound bodies, iVor. 18 !0. 



Ghap. IV. On Elementary Principles - - - - - 221 
Section 1. On Oxygen --_----- 225 

2. On Hydrogen .------. 22ft 

3. On Azote or Nitrogene - - - - - 231 

.. 4. On Carbone or Charcoal ----- 234« 

. 5, On Sulphur 238 

■ 6. On Phosphorus ----..-- 240 
.— 7. On the Metals - 242 

Chap. v. Compounds of two Elements ----- 2C9 

Section 1 . Oxygen ivitk Hydrogen 

Water -.- 270 

Fluoric acid -----.- 277 

Muriatic acid 286 

Oxymuriutic acid ------ 297 

Hyperoxymuriatic acid - - - - 309 

Section 2. Oxygen zvith Azote - - - - - -3l6 

Nitrous gas --------332 

Nitrous oxide - • - - - - -339 

Nitric acid ---343 

Oxynitric acid -----.- 364 
Nitrous acid -------36t> 

Sections. Oxygen uith Carbone - 368 

Carbonic oxide ------- 370 

Carbonic acid - - • - - - -378 

Section 4. Oxygai with Sulphur 

Sulphurous oxide - - - - - -38S 

Sulphurous acid ------ 388 

Sulphuric acid ------- 394 

Skction 5. Oxygen with Phosphorus - . - - - 407 

Phosphorous acid - 403 

Phosphoric acid « - - - - -410 


Section 6. Hj/drogemtftth Azote - - - - - -415 

Ammonia --------. 415 

Section 7. Hydrogen vjilh Carbone 

OUftant gas 437 

Ctirbiirelted Iiydiogen ----- 444 
Section 8. Hydrogen ii-ith Sulphur 

Sulphuretted hydrogen ----- 450 
Supersulphurcttcd hydrogen - - - 453 
Section 9. Hydrogen with Phosphorus 

I'hosphuretted hydrogen - - - - 45G 
Section 10. Curbonc nith Sulphur, with Phosphorus, 

and Sulphur with Phosphorus - - - 462 
Section 11. Fixed Alkalies 

Potash 4GS 

Hydrate of potash - - - - - -475 

Carbonate of potash - - - - - 479 

Potasium or hydrurct of potash - - 4S4 

Soda 492 

Hydrate of soda ... - - 495 

Carbonate of soda ------ 497 

Sodium or hydrurct of soda - - - 502 

Section 12. Earths 504 

Lime ---------- 505 

Magnesia - - - - - - - -512 

Burytcs - - - -- - » - -518 

Strontites - 524 

Al'Jjnine or argil ------ 527 

Silex 536 

Yttria - - - 342 

Glucine --------- 543 

Zirconc --------- 544 

P.xplanation of Plates ----- 546 

/Appendix 5A^ 

{ 221 ) 







XN order to convey a knowledge of chemical 
facts and experience the more clearly, it has 
been generally deemed best to begin with the 
description of such principles or bodies as are 
the most simple, then to proceed to those that 
are compounded of two simple elements, and 
afterwards to those compounded of three or 
more simple elements. This plan will be kept 
in view in the following work, as far as is 
convenient. By elementary principles, or 
simple bodies, we mean such as have not been 
decomposed, but are found to enter into com- 
bination with other bodies. We do not know 


that any one of the bodies denominated ele- 
mentary, is absolutely indecomposable ; but 
it ought to be called simple, till it can be 
analyzed. The principal simple bodies are 
distinguished by the names oxygen, hydrogen, 
azote or nitrogeny carbone or charcoal, sulphur ^ 
phosphorus, and the metals. The fixed alkalis 
and the earths were lately undecomposed ; 
but it has long been suspected that they were 
compounds ; and Mr. Davy has recently 
shewn, by means of galvanic agency, that 
some of them contain metals, and have all the 
characters of metallic oxides ; no harm can 
arise, it is conceived, therefore, from placing 
all the earths in the same class as «he metallic 

After the elementary or simple bodies, those 
compounded of two elements require next to 
be considered. These compounds form a 
highly interesting class, in which the new- 
principles adopted are capable of being exhi- 
bited, and their accuracy investigated by di- 
rect experiment. In ihis class we find several 
of the m.ost important agents in chemistry ; 
namely, water, the sulphuric, nitric, muri- 
atic, carbonic and phosphoric acids, most of 
the compound gases, the alkalis, earths, and 
metallic oxides. 

In the succeeding classes we shall find the 


more complex compounds to consist of 3, 4, 
or more elementary principles, particularly the 
salts ; but in these cases, it generally happens 
that one compound atom unites to one simple 
atom, or one compound to another compound, 
or perhaps to two compound atoms j rather 
than 4 or 6 simple elementary atoms uniting 
in the same instant. Thus the law of che- 
mical synthesis is observed to be simple, and 
always limited to small numbers of the more 
simple principles forming the more com- 



The most simple state in which oxygen can 
be procured, is that of a gas or elastic fluid. 
The gas may be obtained, 

1st. Without the application ofheut. Put 2 
ounces of red lead (minium) into a 5 ounce 
gas bottle ; to which put one ounce of the 
strongest sulphuric acid ; then instantly shake 
it a little to promote mixture, and apply the 
stopper with a bent tube : suddenly a great 
heat is generated, white fumes fill the bottle, 
and a copious flow of gas ensues, which may 


be received in phials over water, in the usual 
way. About 30 cubic inches of gas may be 
expected. This g^s should be exposed to a 
mixture of lime and vi^ater, which absorbs 
about 4- of it (carbonic acid), and leaves the 
rest nearly pure. 

2. With the application of heat. Put 2 
ounces of manganese (the common black oxide) 
into an iron bottle, or gun barrel properly pre- 
pared, to which a recurved tube is adapted. 
This is then to be put into a fire, and heated 
red ; oxygenous gas will come over, and may 
be received as before ; it usually contains a 
small portion of carbonic acid, which may be 
extracted by lime water. Three or four pints 
of air may thus be obtained. 

3. Two ounces of manganese may be put 
into a phial, with the same weight of sulphuric 
acid ; the mixture being made into a paste, 
apply the heat of a candle or lamp, and the 
gas comes over as before, nearly pure, if taken 
over water. 

4. If an ounce of nitre be put into an iron 
bottle, and exposed to a strong red heat, a 
large quantity of gas (2 or 3 gallons) may be 
obtained. It consists of about 3 parts oxygen 
and 1 azote, mixed together. 

5. Put 100 grains of the salt called oxy- 
muriate of potash into a glass or earthenware 


retorl ; apply the heat of a lamp, &;c. till the 
retort grows nearly red, and a quantity of oxy- 
genous gas will come over with great rapidity. 
About 100 cubic inches will be obtained, free 
from carbonic acid, and in other respects 
very pure. 

Various other methods are occasionally used 
to obtain this gas, but the above are the 
principal ; and for one who has not had much 
experience, or who wants only a small quan- 
tity of gas nearly pure, the first and second are 
the easiest and most economical. 

Properties of Oxygen. 

To enumerate all the properties of oxygen, 
and the combinations into which it enters, 
would be to write one half of a treatise on che- 
mistry. It will be sufficient, under the present 
head, to point out some of its more distin- 
guishing features. 

1. It the specific gravity of atmospheric air 
be denoted by 1, that of oxygen will be 1.127 
according to Davy, but some have found it 
rather less. One hundred cubic inches of it, 
at the temperature 55°, and pressure 30 inches 
of mercury, weigh nearly 35 grains; the same 
quantity of atmospheric air weighs 31.1 grains. 
The weight of an atom of oxygen is denoted 


by 7, that of an atom of hydrogen being 1 ; 
this is inferred from the relative weights of those 
elements entering into combination to form 
water. The diameter of a particle of oxygen, 
in its elastic state, is to that of one of hydrogen, 
as .794 to 1 * 

2. Oxygen unites with hydrogen, charcoal, 
azote, phosphorus, and other bodies denomi- 
nated combustible, and that in various man- 
ners and proportions; when mixed with hy- 
drogen and some other elastic fluids, it ex- 
plodes by an electric spark, with noise, and a 
violent concussion of the vessel, together with 
the extrication of much heat. This is called 
detonation. In other cases, the union of oxy- 
gen with bodies is more slow, but accom- 
panied by heat. This is usually called com- 
bustion, as in the burning of charcoal ; and 
v]flammationy when accompanied with flame, 
as in the burning of ozY. — In other cases, the 
union is still more slow, and consequently with 

* For, the diameter of an elastic particle is as ^ y' (weight 
of one atom -f- specific gravity of the fluid). Whence, de- 
noting the weight of an atom of hydrogen by 1, and the 
specific gravity of hydrogenous gas also by 1, the weight 
of an atom of oxygen will be 7, and the specific gravity of 
oxygenous gas, 14-; we have then ^^/ri '• '* ^^ 'v/l • U 
or.TQ^ : I : : diameter of an atom of oxygen : the diameter 
of one of hydrogen. 


little increase of temperature, as in the rusting 
of metals. This is called oxidation. 

Bodies burn in the atmosphere, or air sur- 
rounding the earth, in consequence of the 
oxygen it contains, which is found to be rather 
more than -^th of the whole mass. Hence it is 
not surprising, that in pure oxygen they burn 
with a rapidity and splendor far superior to 
what is observed in ordinary combustion. This 
is easily exhibited, by plunging the ignited 
body into a large phial full of oxygen ; a taper, 
small iron wire, charcoal, and above all phos- 
phorus, burns with inconceivable brilliancy in 
this gas. — The nature of the new compounds 
formed, will be best considered after the pro- 
perties of the other elementary principles have 
been enumerated. 

3. That part of the atmosphere which is ne- 
cessary to the support of animal life, is oxy- 
genous gas. Hence, an animal can subsist 
much longer in a given quantity of pure oxy- 
genous gas, than in the same quantity of com- 
mon or atmospheric air. In the process of 
respiration, a portion of oxygenous gas dis- 
appears, and an equal one of carbonic acid is 
produced j a similar change takes place in the 
combustion of charcoal ; hence it is inferred, 
that respiration is the source of animal heat. 
Atmospheric air inspired, contains about 21 


per cent, oxygenous gas ; the air expired, usu- 
ally contains about 17 per cent, oxygen, and 4 
carbonic acid. But if a full expiration of air 
be made, and the last portion of the expired 
air be examined, it will be found to have 8 or 
9 per cent, carbonic acid, and to have lost the 
same quantity of oxygenous gas. 

4. Oxygenous gas is not sensibly affected by 
continually passing electric sparks or shocks 
through it ; nor has any other operation been 
found to decompose it. 



Hydrogenous gas may be procured by tak- 
ing half an ounce of iron or zinc filings, turn- 
ings, or other small pieces of these metals, 
putting them into a phial, wirh two or three 
ounces of water, to which pour one quarter as 
much sulphuric acid, and an effervescence 
will be produced, with abundance of the gas, 
which may be received over water in the 
usual way. 

Some of its distinguishing properties are : — 
1. It is the lightest gas with which we 
are acquainted. Its specific gravity is nearly 
.0805, that of atmospheric air being 1. This 

Properties of hydrogen. 229 

is nearly the mean attained from the resuUs of 
different philosophers. Whence we find, that 
100 cubic inches of this gas weigh nearly 24 
grains at the mean temperature and pressure. 
It may be stated 10 be tV^^ of the weight of 
oxygen, and -r^th that of azote, and nearly 
the same fractional part of the weight of com- 
mon air. The weight of an atom of hydrogen 
is denoted by 1, and is taken for a standard of 
comparison for the other elementary atoms. 
The diameter of an atom of hydrogen, in its 
elastic state, is likewise denoted by unity, 
. and considered as a standard of comparison 
for the diameters of the atoms of other elastic 

2. It extinguishes burning bodies, and is 
fatal to animals that breathe it. 

3. If a phial be filled with this gas, and a 
lighted taper, or red hot iron, be brought to 
its mouth, the gas will take fire, and burn 
gradually till the whole is consumed. The 
flame is usually reddish, or yellowish white. 

4. When oxygen and hydrogen gas are 
mixed together, no change is perceived ; but 
if a lighted taper is brought to the mixture, or 
an electric spark passed through it, a violent 
explosion takes place. The two gases unite 
in a proportion constantly the same, and pro- 
duce steam, which in a cold medium is in- 


stantly condensed into water. When 2 mea- 
sures of hydrogen are mixed with 1 of oxygen, 
and exploded over water, the whole gas dis- 
appears, and the vessel becomes filled with 
water, in consequence of the formation and 
subsequent condensation of the steam. 

If 2 measures of atmospheric air be mixed 
with I of hydrogen, and the electric spark 
made to pass through the mixture, an explo- 
sion ensues, and (he residuary gas is found to 
be lA measures, consisting of azote and a small 
portion of hydrogen. The portion of the mix- 
ture which disappears, \^, being divided by 
3, gives 42 nearly, denoting the oxygen in 
two measures of atmospheric air, or 21 per 
cent. The instrument for exploding such mix- 
tures in is called V olio's eiidioyneter. 

5. Another remarkable property of hydrogen 
deserves notice, though it is not peculiar to it, 
but belongs in degree to all other gases that 
differ maierially from atmospheric air in spe- 
cific gravity ; if a cylindrical jar of 2 or more 
inches in diameter, be filled with hydrogen, 
placed upright and uncovered for a moment or 
two, nearly the whole will vanish, and its 
place be supplied by atmospheric air. In this 
case it must evidently leave the vessel in a 
body, and the other enter in the same manner. 
But if the jar of hydrogen be held with its 


mouth downwards, It slowly and gradually 
wastes away, an.d atmospheric air enters in the 
same manner ; after several minutes there will 
be found traces of hydrogen remaining in the 
jar. If a tube of 12 inches long and -^ inch 
internal diameter, be filled with hydrogen, 
there is little difference perceived whether it is 
held up or down ; the gas slowly and gradually 
departs in each case, and as much may be 
found after 10 minutes have expired, as would 
be after 2 or 3 seconds if the tube were an 
inch or more in diameter. If a 3 or 4 ounce 
phial be filled with hydrogen, and a cork 
adapted, containing a tube of 2 or 3 inches 
long and -pV ^"^^"^ internal diameter, it does not 
make any material difference in the waste of 
the gas whether the phial is held up or down ; 
ir will be some hours before the hydrogen gets 

6. Hydrogen gas bears electrification with- 
out any change. 



Azotic or nitrogene gas may be procured 
from atmospheric air, of which it constitutes 
the greater part, by various processes : 1st. To 


100 measures of atmospheric air put 30 of 
nitrous gas ; the mixture having stood some 
time, must be passed two or three times 
through water ; it will still contain a small 
portion of oxygen ; to the residuum put 5 more 
measures of nitrous gas, and proceed as before ; 
small portions of the residuum must then be 
tried separately, by nitrous gas and by atmo- 
spheric air, to see whether any diminution 
takes place ; whichever produces a diminution 
after the mixture, shews that it is wanting, 
and the other redundant ; consequeritly a small 
addition to the stock must be made accord- 
ingly. By a few trials the due proportion may 
be found, and the gas being then well washed, 
may be considered as pure azotic. 2. If a 
quantity of liquid sulphuret of lime (a yellow 
liquid procured by boiling one ounce of a mix- 
ture of equal parts sulphur and lime in a quart 
of water, till it becomes a pint) be agitated in 
2 or 3 times its bulk of atmospheric air for some 
time, it will take out all the oxygen, and leave 
the azotic gas pure. 3. If to 100 measures of 
atmospheric air. 42 of hydrogen be put, and 
an electric spark passed through the mixture, 
an explosion will take place, and there will be 
left 80 measures of azotic gas, &c. 
The properties of this gas are ; — 
1. The specific gravity of azotic gas at the 


temperature of 55° and pressure 30 inches, is 
.967 according to Davy, that of air being 1. 
The weight of 100 cubic inches is nearly 30 
grains. The weight of an atom of azote is 
denoted by 5, that of an atom of hydrogen 
being 1 ; this is inferred chiefly from the com- 
pound denominated ammonia, and from those 
of azote and oxygen, as will be seen here- 
after. The diameter of a particle of azote in 
its elastic state, is to that of one of hydrogen, 
as .747 to I. 

2. Like hydrogen, it extinguishes burning 
bodies, and is fatal to animals that breathe it. 

3. Azotic gas is less prone to combination 
than most, if not all, other gases ; it never 
combines with any other gas simply of itself; 
but if a mixture of it and oxygen has the 
electric spark passed through it for a long con- 
tinuance, a slow combustion of the azote takes 
place, and nitric acid is formed. In other 
cases azote may be obtained in combination 
with oxygen in various proportions, and the 
compounds can be analyzed, but are not so 
easily formed in the synthetic way. 

4. Azotic gas, as has been noticed, consti- 
tutes nearly ^-ths of atmospheric air, notwith- 
standing its being fatal to animals that breathe 
it in its unmixed state ; the other ith is oxy- 
genous gas, which is merely mixed with and 


diffused through the former, and this mixture 
constitutes the principal part of the atmosphere, 
and is suited, as we perceive, both for animal 
life and combustion. 

5. Azotic gas is not affected by repeated 



If a piece of wood be put into a crucible, 
and covered with sand, and the whole gra- 
dually raised to a red heat, the wood is de- 
composed ; water, an acid, and several elastic 
fluids are disengaged, particularly carbonic 
acid, carburetted hydrogen, and carbonic oxide. 
Finally, there remains a black, brittle, porous 
substance in the crucible, called charcoal, 
which is incapable of change by heat in close 
vessels, but burns in the open air, and is con- 
verted into an elastic fluid, carbonic acid. 
Charcoal constitutes from 1 5 to 20 per cent, of 
the weight of the wood from which it was 

Charcoal is insoluble in water ; it is without 
taste or smell, but contributes much to correct 
putrefaction in animal substances. It is less 
liable to decay than wood by the action of air 


and water. When new, it gradually absorbs 
moisture from the atmosphere, amounting to 
12 or 15 per cent, of its weight. One half of 
the moisture may be expelled again by the 
heat of boiling water, if long continued ; the 
other requires a higher temperature, and then 
carries with it a portion of charcoal. 1 took 
350 grains of charcoal that had been exposed 
to the atmosphere for a long time ; this was 
subjected to the heat of boiling water for one 
hour and a half ; it lost 7 grains in the first 
quarter of an hour, 6 in the second, and finally 
it had lost 25 grains. 

Several authors have maintained that char- 
coal, after being heated red, has the property 
of absorbing most species of elastic fluids, in 
such quantities as to exceed its bulk several 
times ; by which we are to understand a che- 
mical union of the elastic fluids with the char- 
coal. The results of their experiments on this 
head, are so vague and contradictory, as to 
leave little credit even to the fact of any such 
absorption. 1 made 1500 grains of charcoal 
red hot, then pulverized it, and put it into 
a Florence fiask with a stopcock ; to this a 
bladder filled with carbonic acid was con- 
nected ; this experiment was continued for a 
week, and occasionally examined by weighing 
the flask and its contents. At first there ap- 


peared an increase of weight of 6 or 7 grains, 
from the acid mingling with the common air 
in the flask, of less specific gravity j but the 
succeeding increase was not more than 6 
grains, and arose from the moisture which 
permeated the bladder : for the bladder 
continued as distended as at first, and finally 
upon examination was found to contain no- 
thing but atmospheric air. Yet carbonic acid 
is stated to be the most absorbable by char- 
coal. One of the authors above alluded to, 
asserts that the heat of boiling water is sufH- 
cient to expel the greater part of the gases so 
absorbed. Now this is certainly not true, as 
Allen and Pepys have shewn ; and most prac- 
tical chemists know that no air is to be obtained 
from moist charcoal below a red heat. Hence 
the weight acquired by fresh made charcoal, 
is in all probability to be wholly ascribed to 
the moisture which it absorbs from the atmo- 
sphere i and it is to the decomposition of this 
water, and the union of its elements with char- 
coal, that we obtain such an abundance of 
gases by the application ot a red heat. 

It was the prevailing 0()inion some time 
nrro that charcoal was an oxide of diamond^ 
but Mr. Tennant, and more recently Messrs. 
Allen and Pepys, have shewn that the same 
quantity of carbonic acid is obtained from the 


combustion of the diamond as from that of an 
equal weight of charcoal j we must therefore 
conclude, that the diamond and charcoal are 
the same element in different states of aggre- 

Berthollet contends that charcoal contains 
hydrogen ; this doctrine is farther counte- 
nanced by some experiments of Berthollet jun. 
in the Annales de Chimie, Feb, 1807; Mr. 
Davy's experience seems also on the same side. 
But their observations do not appear to me to 
warrant any other conclusion than that it is 
extremely difficult to obtain and operate upon 
charcoal entirely free from water. Hydrogen 
appears no more essential to charcoal than air 
is essential to water. 

From the various combinations of charcoal 
with other elements hereafter to be mentioned, 
the weight of its ultimate particle is deduced 
to be 5, or perhaps 5.4, that of hydrogen being 
denoted bv unity. 

Charcoal requires a red heat, just visible bj' 
day light, to burn it : this corresponds to lOOQ" 
of Fahrenheit nearly. 




Sulphur or brimstone is an article well 
known ; it is an element pretty generally dis- 
seminated, but is most abundant in volcanic 
countries, and in certain minerals. A great 
part of what is used in this country is imported 
from Italy and Sicily ; the rest is obtained from 
the ores of copper, lead, iron, Src. 

Sulphur is fused by a heat a little above that 
of boiling water. It is usually run into cylin- 
drical molds, and upon cooling becomes roU 
sulphur. In this case the rolls become highly 
electrical by friction : they are remarkably 
brittle, frequently falling in pieces by the con- 
tact of the warm hand. Its specific gravity is 
1.98 or 1.99. 

Sulphur is sublimed by a heat more than 
sufficient to fuse it ; the sublimate constitutes 
the common fioxvers of sulphur. The effects 
of the different gradations of heat on sulphur 
are somewhat remarkable. It is fused at 226° 
or 228° oi Fahrenheit, into a thin fluid ; it be- 
gins to grow thick, darker, and viscid at 
about 350°, and continues so till 600° or up- 
wards, the fumes becoming gradually more 


copious. This viscid mass, if poured into wa- 
ter, continues to retain a degree of tenacity 
after being cooled ; but finally it becomes of a 
hard and smooth texture, much less brittle than 
common roll sulphur. 

For any thing certainly known yet, sulphur 
appears to be an elementary substance. It 
enters into composition with various bodies ; 
and from a comparison of several compounds, I 
deduce the weight of an atom of sulphur to be 
nearly 14 times that of hydrogen j it is possible 
it may be somewhat more or less, but I think 
the error of the above cannot exceed 2. Mr, 
Davy seems to conclude, from galvanic expe- 
riments on sulphur, that it contains oxygen j 
this may be the case, from the great weight of 
the elementary particles ; but it should contain 
50 per cent, oxygen, or none at all. 

Berthollet jun. seems to conclude that sul- 
phur contains hydrogen (Annal. de Chimie, 
Feb. 1807). Mr. Davy inclines to this idea 
{Philos. Transac. 1807). That some traces of 
hydrogen may be discovered in sulphur there 
cannot be much doubt. Dr. Thomson has 
well observed the difficulty of obtaining sul- 
phur free from sulphuric acid ; but if sulphu- 
ric acid be present, water must also be found, 
and consequently hydrogen. A strong argu- 
ment against the existence of hydrogen as an 


essential in sulphur, is derived from the consi- 
deration of the low specific heat of sulphur. 
If this article contained 7 or 8 per cent, of 
hydrogen, or 50 per cent, of oxygen, or as 
much water, it would not have the low spe- 
cific heat of .19. 

Sulphur burns in the open air at the tempe- 
rature of 500° ; it unites with oxygen, hydro- 
gen, the alkalis, earths and metals, forming a 
great variety of interesting compounds, which 
will be considered in their respective places. 



Phosphorus is an article having much the 
same appearance and consistency as white 
wax. It is usually prepared from the bones of 
animals, which contain one of its compounds, 
phosphate of lime, by a laborious and complex 
process. The bones are calcined in an open 
fire; when reduced to powder, sulphuric acid 
diluted with water is added j this acid takes 
part of the lime, and forms an insoluble com- 
pound, but detaches superphosphate of lime, 
which is soluble in water. This solution is 
evaporated, and the salt is obtained in a glacial 
state. The solid is reduced to powder, and 


mixed with half its weight of charcoal ; then 
the mixture is put into an earthenware retort, 
and distilled by a strong red heat, when the 
phosphorus comes over, and is received in the 
water into which the tube of the retort is 

Phosphorus is so extremely inflammable, 
that it is required to be preserved in water : 
It melts about blood heat ; and in close ves- 
sels it can be heated up to 550°, when it boils, 
and of course distils. When exposed to the 
air, it undergoes slow combustion ; but if 
heated to 100° or upwards, it is inflamed, 
burns with rapidity and the emission of great 
heat, accompanied with white fumes. It com- 
bines with oxygen, hydrogen, sulphur and 
other combustible bodies, and with several of 
the metals. 

Phosphorus is soluble in expressed and other 
oils, in alcohol, ether, &c. ; these solutions, 
when agitated with common air or oxygenous 
gas, appear luminous in the dark : a portion 
of the oil being rubbed upon ihe hand, makes 
it appear luminous. 

The specific gravity of phosphorus is 1.7 
nearly : the weight of its ultimate particle or 
atom is about 9 times that of hydrogen, as will 
appear when its compounds with oxygen are 




The metals at present known, amount at 
least to 30 in number ; they form a class of 
bodies which are remarkably distinguishable 
from others in several particulars, as well as 
from each other. 

Gravity. One of the most striking pro- 
perties of metals is their great weight or specific 
gravity. The lightest of them (excluding the 
lately discovered metals, potasium and sodium) 
weighs at least six times as much as water, and 
the heaviest of them 23 times as much. On 
the supposition that all aggregates are consti- 
tuted of solid particles or atoms, each sur- 
rounded by an atmosphere of heat, it is a cu- 
rious and important enquiry, whether this su- 
perior specific gravity of the metals is occa- 
sioned by the greater specific gravity of their 
individual solid particles, or from the greater 
number of them aggregated into a given vo- 
lume, owing to some peculiar relation they 
may have to heat, or their superior attraction 
for each other. Upon examination of the facts 
exhibited by the metals, in their combinations 


with oxygen, sulphur, and the acids, it will 
appear that the former of these two positions 
is the true one , namely, that the atoms of 
metals are heavier, almost in the same ratio as 
their specific gravities : thus an atom of lead 
will be found to be 11 or 12 times heavier 
than one of water, and its specific gravity is 
equally so. It must however be admitted, 
that in metals and other solid bodies, as well 
as in gases, their specific gravities are by no 
means exactly proportional to the weights of 
their atoms. It is further remarkable of the 
metals, that notwithstanding the great weight 
of their ultimate particles relatively, those par- 
ticles possess no more, but often ]ess, heat 
than particles of hydrogen, oxygen, or water. If 
the heat surrounding a particle of water of any 
temperature be denoted by 1, that surrounding 
a particle of lead will be found only \ as much, 
though the atom of lead is 12 times the weight 
of that of water. One would be apt to con- 
clude from this circumstance, that an atom of 
lead has less attractive power for heat than an 
atom of water ; but this does not necessarily 
follow ; nay, the reverse is perhaps more pro- 
bable of the two ; for, the absolute quantity 
of heat around anv one particle in a state of 
aggregation, depends greatly upon the force 
of affinity, or the attraction of aggregation ; 


if this be great, the heat is partly expressed or 
squeezed out ; but if little, it is retained^ 
though the attraction ot the particles for heat 
remains unaltered. An atom of water may 
have the same attraction for heat that one of 
lead has ; but the latter may have a stronger 
attraction of aggregation, by which a quantity 
of heat is expelled, and consequently less heat 
retained by any aggregate of the particles. 

Opacilij and Lustre. Metals are remark- 
ably opake, or destitute of that property which 
glass and some other bodies possess, of trans- 
mitting light. When reduced to leaves as 
thin as possible, such as gold and silver leaf, 
they continue to obstruct the passage of light. 
Though the metallic atoms, with their atmo- 
spheres of heat, are ncarlv the same size as the 
atoms of water and their atmospheres, yet it 
seems highly probable that the metallic atoms 
abstracted from their atmospheres, are much 
larger than those of water in like circumstances. 
The former, 1 conceive, are large particles 
with highly condensed atmospheres , the lat- 
ter, arc small particles with more extensive 
atmospheres, because of their less powerful 
attraction for heat. Hence, it may be sup- 
posed, the opacity of metals and their lustre 
are occasioned. A great quantity of solid 
matter and a high condensation of heat, are 


likely to obstruct the passage of light, and to 
reflect it. 

Malleability and Ductility. Metals are dis- 
tinguished for these properties, which many of 
them possess in an eminent degree. By means 
of a hammer, they may be flattened and ex- 
tended without losing their cohesion, especially 
if assisted by heat. Cylindrical rods of metal 
can be drawn through holes of less diameter, 
by which they are extended in length ; and 
this successively til! they form very small wire. 
These properties render them highly useful. 
Metals become harder and denser by being 

Tenacity. Metals exceed most other bodies 
in their tenacity or force of cohesion ; however 
they differ materially from each other in this 
respect. An iron wire of -rVth of an inch in 
diameter, will support 5 or 6 hundred pounds. 
Lead is only T-'^th part as strong, and not equal 
to some sorts of wood. 

Fusibility. Metals are fusible or capable of 
being melted by heat ; but the temperatures 
at which they melt are extremely different. 

Most of the medals possess a considerable 
degree of hardness ; and some of them, as iron, 
are susceptible of a high degree of elasticity ; 
they are mostly excellent conductors of heat 
and of electricity. 


Metals combine with various portions of 
oxygen, and form metallic oxides ; they also 
combine with sulphur, and form sidphurets ; 
some of them with phosphorus, and form p}ios- 
phiirets ; with carbone or charcoal, and form 
carburets^ &c. which will be treated of in their 
respective places. Metals also form compounds 
one with another, called alloys. 

The relative weights of the ultimate particles 
of the metals may be investigated, as will be 
shewn, from the metallic oxides, from the me- 
tallic sulphurets, or from the metallic salts ; 
indeed, if the proportions of the several com- 
pounds can be accurately ascertained, I have 
no doubt they will all agree in assigning the 
same relative weight to the elementary particle 
of the same metal. In the present state of our 
knowledge, the results approximate to each 
other remarkably well, especially where the 
different compounds have been examined with 
care, and can be depended upon ; but the pro- 
portions of the elements in some of the metallic 
oxides, sulphurets, and salts, have not yet been 
found with any degree of precision. 

The number of metals hitherto discovered is 
30, including the two derived from the fixed 
alkalis ; some of these may, perhaps, be im- 
properly denominated metals, as they are 
scarce, and have not been subjected to so much 


experience as others. The greater part of these 
metals have been discovered within the last 
century.. Dr. Thomson divides the metals into 
4 classes; 1. Malleable metals : 2. Brittle and 
easily fusible metals : 3. Brittle and difficultly 
fusible metals : 4. Refractory metals ; that is, 
such as are known only in combination, it 
having not yet been found practicable to ex- 
hibit them in a separate state. — They may be 
arranged as follows : 

1. Malleable. 

1. Gold. 9. Copper. 

2. Platinum. 10. Iron. 

3. Silver. 11. Nickel. 

4. Mercury. 12. Tin. 

5. Palladium. 13. Lead. 

6. Rhodium. 14. Zinc. 

7. Iridium. 15. Potasium. 

8. Osmium. 16. Sodium. 

2. Brittle and easily fusible. 

1. Bismuth. 3. Tellurium. 

2. Antimony. 4. Arsenic. 

3. Brittle and difficultly fused. 
i. Cobalt. 4. Molybdenum. 

2. Manganese. 5. Uranium. 

3. Chromium. 6. Tungsten, 


4. Refractory. 

1. Titanium. 

2. Columbium. 

3. Tantalium. 

4. Cerium. 

To which last class also may the supposed 
metals from the earths be referred. 

Tiic following Table exhibits the chief properties of the 
metals in an absolute as well as comparative point of 








Sp. Gr. 









32« W 


Plat in. 












22« W 







—39" F 

Pal lad. 










27o W 










158^ W 






25? 50? 







410" F 







612« F 







680« F 







80° F 






150" F 


red wh 




4760 -p 



grey w. 




810° F 



blue w. 




blue w. 









7 811 

55 i 


1 30" \V 
160° W 



yel. w. 



iron gr. 





yel. w. 


170" + \V 


grey w. 










170 +W 


170 +W 
170 +\V 




More particular Properties of the Metals, 

Gold. This metal has been known from 
the earliest times, and always highly valued. 
Its scarcity, and several of its properties, con- 
tribute to make it a proper medium of ex- 
change, which is one of its chief uses. Eng- 
lish standard gold consists of 1 1 parts by- 
weight of pure gold, and 1 part of copper (or 
silver) alloyed. This is usually spoken of as 
being 22 carats fine, pure gold being 24 carats 
fine. The use of the copper is to render the 
alloy harder, and consequently more durable 
than pure gold. 

Gold retains its splendid yellow colour and 
lustre in all states of the atmosphere unchanged. 
Its specific gravity, when pure, and ham- 
mered, is 19.3, or more; but that of the same 
gold, in other circumstances, may be 19.2. — 
The specific gravity of standard gold varies 
from 17.1 to 17.9, accordingly as it is alloyed 
with copper, copper and silver, or silver, as 
well as from other circumstances. It excels 
all other metals in malleability and ductility ; 
it may be beaten out so thin, that a leaf weigh- 
ing 1 grain, shall cover 50 or 60 square inches, 
in which case the leaf is only -^-y ^'aoa th part of 
an inch in thickness : but it is capable of be- 


ing reduced to ■y\th of that thickness on silver 
wire. Gold melts at 32" of AVedgwood's py- 
rometer ; that is, a red heat, but one greatly 
inferior to what mav be obtained bv a smith's 
forge : when fused, it may continue in that 
state for several weeks without losing any ma- 
terial weight. There is reason to believe that 
gold combines with oxygen, sulphur, and 
phosphorus ; but those compounds are diffi- 
cultly obtained. It combines with most of 
the metals, and forms alloys of various de- 

The weight of an atom of gold is not easily 
ascertained, because of the uncertainty in the 
proportions of the elements forming the com- 
pounds into which it enters. It is probably 
not less than 140, nor more than 200 times the 
weight of an atom of hydrogen. 

Platina. This metal has not been found 
any where but in South America. In its crude 
state, it consists of small flattened grains of a 
metallic lustre, and a grey-while colour. This 
ore is found to be an alloy of several metals, 
of which platina is usually the most abundant. 
The grains are dissolved in nitro-muriatic acid, 
except a black matter which subsides ; the 
clear liquor is decanted, and a solution of sal 
ammoniac is dropped into it : a yellow preci- 
pitate falls j this is heated to redness, and the 


powder is platina nearly pure. To obtain it 
SI ill more pure, the process must i)e repeated 
upon this platina. When these grains are 
wrapped up in a thin plate of platina, heated 
to redness, and cautiously hammered, they 
unite and form a solid mass of malleable metal. 

PlaUna thus obtained, is of a white colour, 
rather inferior to silver. In hardness it some- 
what exceeds silver ; but in specific gravity 
it exceeds all other bodies hitherto known. 
Specimens of it, when hammered, have been 
found of the specific gravity of 23 or upwards. 
It is nearly as ductile and malleable as gold. 
It requires a greater heat than most metals to 
fuse it ; but when heated to whiteness, it 
welds in the same manner as iron. It is not 
in any degree altered by exposure lo the air or 
to water. No ordinary artificial heat seems 
capable of burning it or uniting it to oxygen. 
Its oxidizement, however, may be effected 
by means of galvanism and electricity, and by 
exposing it to the heat excited by the com- 
bustion of hydrogen and charcoal in oxygenous 
gas. Platina has been united to phosphorus, 
but not to hydrogen, carbone, or sulphur. It 
unites with most of the metals to form alloys. 

The weight of the ultimate particle of pla- 
tina cannot be ascertained from the data we 
have at present : from its combination with 

252 SILVER. 

oxygen, it should seem to be about 100 ; but, 
judging from its great specific gravity, one 
would be inclined to think it must be more. 
Indeed the proportion of oxygen in the oxides 
of platina cannot be considered as ascertained. 

Platina is chiefly used for chemical pur- 
poses ; in consequence of its infusibility, and 
the difficulty of oxidizing it, crucibles and 
other utensils are made of it, in preference to 
every other metal. Platina wires are extremely 
useful in electric and galvanic researches, for 
like reasons. 

Silver. This metal is found in various parts 
of the world, and in various combinations ; 
but the greatest quantity is derived from Ame- 
rica. Its uses are generally known. The 
speciHc gravity of melted silver is 10.474 ; after 
being hammered, 10.511. English standard 
silver, containing -j^^ copper, simply fused, is 
10.2. Pure silver is extremely malleable and 
ductile ; but inferior in these respects to gold. 
It melts at a moderately red heat. It is not 
oxidized by exposure to the air, but is tar- 
nished or loses its lustre, which is occasioned 
by the sulphureous vapours floating in the air. 
It unites with sulphur in a moderate heat -, 
and may be oxidized by means of galvanism 
and electricity ; it burns with a green flame. 


Silver combines with phosphorus, and forms 
alloys with most of the metals. 

The relative weight of an atom of silver 
admits of a pretty accurate approximation, 
from the known proportions of certain com- 
pounds into which silver enters ; namely, the 
oxides and sulphuret of silver, and the salts of 
silver : all of these nearly concur in deter- 
mining the weis:ht ot an atom of silver to be 
100 times that of hydrogen. 

Mercury. This metal, which is also 
known under the name of quicksilvey\ has 
been long discovered and in use. It is white 
and brilliant, reflecting more light from its 
surface, perhaps, than any other metal. Its 
specific gravity is 13.58. It is fluid at the 
common temperature of the atmosphere ; but 
it congeals when reduced to the temperature 
of — 39° Fahrenheit. It contracts suddenly at 
the point of congelation, contrary to what is 
exhibited in water ; when congealed, mer- 
cury becomes malleable ; but its qualities in a 
solid state are not easily to be ascertained. 
When heated in the operi air to the tempera- 
ture of 660°, or thereabouts, according to the 
equidifferentia! scale, mercury boils, and dis- 
tils rapidly ; like water, however, it rises in 
vapour in a greater or less degree at all tempe- 
ratures. Pure liquid mercury has no taste nor 


smell ; it may be taken internally, without 
producing any remarkable effect on the human 
body. It can be united with oxygen, sulphur, 
and phosphorus ; and it forms alloys, or, as 
they are more commonly called, qmalgams^ 
with most of the metals. 

The weight of an atom of mercury is deter- 
minable from its oxides, its sulphuret, and the 
various salts which it forms with acids : from 
a comparison of all which, it seems to be about 
167 times the weight of hydrogen. From any 
thing certainly known, the mercurial atom is 
heavier than any other ; though there are two 
or three metals which exceed it in specific 

Palladium. This metal was discovered a 
few years ago in crude platina, by Dr. Wollas- 
ton, of which an account may be seen in the 
Philos. Transact, for 1804. Jt is a white 
metal, resembling platina in appearance, but 
is much harder : it is only one half of the spe- 
cific gravity of platina. It requires great heat 
to fuse it, and is difficultly oxidized. Palla- 
dium combines with oxygen and sulphur, and 
forms alloys with several of the metals. But 
we have not yet sufficient data to determine 
the weight of its ultimate particles. 

Rhodium. This metal has been discovered 
still more recently than the last in crude pla- 


tina, by Dr. Wollaston. — It constitutes about 
^liyth part of crude platiiia. It possesses nearly 
the same colour and specific gravity as palla- 
dium, and agrees with it in other paiticulars ; 
but in certain respects they appear to possess 
essentially distinct properties.-^The weight of 
the ultimate particles of this metal cannot yet 
be ascertained. 

Iridium and Osmium. These two metals 
were lately discovered by Mr. Smithscn Ten- 
nant to exist in crude platina. When crude 
platina is dissolved in nitro-muriatic acid, 
there remains a quantity of black shining 
powder ; this, powder contains two metals, 
one of which Mr. Tennant called Iridium^ 
from the variety of colours which its solutions 
exhibited ; the other Osmhmiy from a peculiar 
smell which accompanies its oxides. Iridium 
is a white metal, infusible as platina, diflicultly 
soluble in any acid : it seems to combine with 
oxygen, and to form alloys with some of the 
metals. Osmium has a dark grey or blue co- 
lour : when heated iii the air, it combines 
with oxyg-en, and the oxide is volatile, posses- 
sing the characterrstic smell. In a close vessel, 
it resists any heat that has been applied ; it 
also resists the action of acids, but unites with 
potash. It amalgamates with mercury. The 


welfrhts of the atoms of these two metals are 

Copper. This metal has been long known. 
It is of a fine red colour ; its taste is styptic 
and nauseous. Its specific gravity varies from 
8.6 to 8.9. It possesses great ductility, can 
be drawn into wire as fine as hair, and is ca- 
pable of being beaten into very thin leaves. 
It is fused in a temperature higher than silver, 
and lower than gold, about 27° of Wedg- 
wood's thermometer. Copper unites with 
oxygen, sulphur, and phosphorus ; and forms 
alloys v.'ith several other metals. 

The weight of the ultimate particle of cop- 
per, may be ascertained with considerable pre- 
cision, from the proportions in which it is 
found combined with oxygen, sulphur, and 
phosphorus ; as well as from its combinations 
with the acids. From a comparison of these, 
its weight seems to be nearly 56 times that of 

Iron. This metal, the most useful we are 
acquainted with, has been long known. It 
seerfis to be found almost in every coun'ry, 
and in a great variety of combinations. Its 
ores require great heat to expel the foreign 
matters, and to melt the iron, which is first 
obtained in masses or pigs, called cast iron i 

IRON. 257 

after which it undergoes a laborious operation, 
the object of which is to expel the carbone 
and oxygen which it may yet contain, and to 
render it maHeable. 'Ibis consists chiefly in 
hammering the i/on when heated almost to 

Iron is susceptible of a high j)olish ; it is 
very hard ; it varies in specific gravity from 
7.6 to 7.8. It is distinguishable from all other 
metals, by possessing, in a high degree, (in- 
deed almost exclusively) magnetical attraction. 
The magnet or loadstone itself is chiefly iron, 
with certain modifications. Iron increases in 
malleability as it increases in temperature : its 
ductility is surpassed by few other metals, as 
its wire admits of extension till it becomes as 
fine as human hair: its tenacity, which is one 
of its most valuable properties, is not equalled 
by any other body we are acquainted ^with. 
Pure malleable iron is estimated to melt at 
158° of Wedgwood j whereas cast iron melts 
about 130°. 

Iron is distinguished for its combinations 
with oxygen, carbone, sulphur, and phos- 
phorus : it forms alloys with several of the 
metals, but they are not of much importance. 

I'he weight of an atom of iron may be 
found from almost any of its numerous com- 
binations, either its oxides, its sulphurets, or 


any of the salts which it forms with acids : all 
these will be found to give the same weight 
nearly ; namely, 50 times the weight of an 
atom of hydrogen. 

Nickel. The ore from which this metal is 
obtained, is found in Germany : it usually 
contains several other metals, from which it is 
difficult to extract the nickel in a state of 
tolerable purity. Nickel, when pure as it can 
be obtained, is of a silver white colour ; its 
specific gravity is 8.279, and when forged 
p.. 666. It is malleable, both hot and cold, 
and may be beaten into a leaf of -j.^-^ of an inch 
in thickness. A very great heat is required to 
fuse it. Jt is attracted by the magnet nearly 
as much as iron, and may be converted into a 
magnet itself. It combines with oxygen, sul- 
phur, and phosphorus ; and may be alloyed 
with certain other metals. 

The weight of its atom can scarcely yet be 
determined, for want of a more accurate know- 
ledge of the compounds into which it enters : 
perhaps it will be found to weigh about 25, or 
else double that number, 50. 

Tin. This metal has been long known, 
though it is found but in few places compara- 
tively. Cornwall is the only part of Great 
Britain where this metal abounds ; and its tin 
mines are the most celebrated in Europe. Tin 

LEAD. 259 

is a white metal, nearly resembling silver ; its 
specific gravity is about 7.3. It is malleable 
in a high degree ; but inferior to many metals 
in ductility and tenacity. It melts at the low 
temperature of 440° Fahrenheit. When ex- 
posed to the air, it loses its lustre, and be- 
comes grey ; this is more rapidly the case if it 
be melted ; its surface then soon becomes grey, 
and in time passes to yellow. Tin combines 
with oxygen, salphur, and phosphorus, and 
forms allovs with most of the metals. 

The weight of an atom of tin may be de- 
rived from the proportion of the elements in 
the oxides, the sulphuret or the phosphuret of 
tin ; or from the salts of tin. It is probably 
about 50 times heavier than hydrogen. 

Lead. This metal seems to have been 
known in early times : it is of a blueish white 
colour, bright when recently melted, but soon 
loses its lustre when exposed to the air. It has 
scarcely any taste or smell ; but operates as a 
deadly poison when taken internally : it seems 
to benumb the vital functions, and to destroy 
the nervous sensibility, inducing a paralysis, 
and finally death. The specific gravity of 
lead, whether hammered or not, is about 11.3 
or 11.4 J it is n)alleable, and may be reduced 
to thin plates. It melts about 610° of Fahren- 
heit. It combines with oxygen, sulphur, and 


phosphorus, and forms alloys with most other 

The ultimate particle of lead, as deduced 
from a comparison of its oxides, suiphuret, and 
the salts in which it is found, I estimate at 95 
times that of hydrogen. 

Zinc The ores of this metal are not rare ; 
but the metal has not been extracted from them 
in a pure state, at least in Britain, much more 
than half a century. Zinc is a brilliant white 
metal, inclining to blue. Its specific gravity 
is from 6.9 to 7 2. It was till lately considered 
as a brittle metal ; but Messrs. Hobson and 
Sylvester, of Sheffield, have discovered that 
between the temperature of 210° and 300°, 
zinc yields to the hammer, may be laminated, 
wire drawn, &c. and that after being thus 
wrought, it continues soft and flexible. It 
melts about 680°, and above that temperature 
evaporates considerably. Zinc soon loses its 
lustre in the air, and grows grey ; but in wa- 
ter it becomes black, and hydrogen gas is 
emitted. Zinc combines with oxygen ; and 
either it or its oxides combine with sulphur 
and phosphorus. It fbrms alloys with most of 
the metals, some of which are very useful. 

The atom of zinc weighs nearly 56 times as 
much as hydrogen. 

PoTAsiuM. We are principally indebted to 


Mr. Davy for our knowledge of this metal ; its 
oxide, potash, or the fixed vegetable alkali, 
is universally known j but the decomposition 
of the oxide is a recent discovery. To obtain 
the metal, a small piece (30 or 40 grains) of 
pure caustic potash, which has been exposed 
to the air a few moments, to acquire a slight 
deigree of moisture, sufficient to render it a 
conductor of galvanism, is to be exposed to 
the action of a powerful galvanic battery j by 
its operation, the oxygen of the potash is ex- 
pelled, and fluid metallic globules of the ap- 
pearance of mercury, are obtained. This 
metal has also been produced by Messrs. Gay 
Lussac and Thenard, by exposing potash to 
iron turnings in a white heat : some potasium 
was obtained, and an alloy of potasium and 
iron. Mr. Davy has made an experiment 
with a similar result ; and found that a large 
quantity of hydrogen gas is at the same time 
given out. This fact seems to point out pot- 
ash as a compound of potasium and water, 
and not of potasium and oxygen ; the French 
chemists argue that potasium is a compound of 
hydrogen and potash ; but, as Mr. Davy pro- 
perly observes, their argument amounts to this, 
that potasium is a compound of hydrogen and 
an unknown base, which compound united to 
oxygen forms potash. This subject must be 

262 SODIUM. 

left to future experience. — Potasium, at the 
temperature of 32°, is solid and brittle ; and 
its fragments exhibit a crystallized texture : at 
50°, it is soft and malleable ; at 60", it is im- 
perfectly fluid ; at 100% it is perfectly fluid, 
and small globules unite as in mercury, ft 
may be distilled by a heat approaching to red- 
ness. Its specific gravity is only 6 ; this cir- 
cumstance would seem to countenance the 
notion of its containing hydrogen. Potasium 
combines with oxygen, sulphur, and phos- 
phorus ; and it seems to form alloys with many 
of fhe metals. 

The weight of an atom of potasium appears 
from its combination with oxygen to be 35 
times that of hydrogen. 

Sodium. Mr. Davy obtained this metal 
from the fixed mineral alkali, or soda, by 
means of galvanism, in the same way as pota- 
sium. Sodium, at the common temperature, 
is a solid, white melal, having the appearance 
of silver -, it is exceedingly malleable, and 
much softer than other metallic substances. 
Its specific gravity is rather less than water, 
being 9348. It begins to melt at 120% and 
is perfectly fluid at 180^. It combines with 
oxygen, sulphur, and phosphorus j and forms 
alloys with the metals. 

The weight of an atom of sodium, as de- 


duced from its combination with oxyj^en. is 
nearly 21 times ihe weight of hydrogen. 

Bismuth. This has not been known as a 
distinct metal much more than a century. Its 
ores are found chiefly in Germany. — Bismuth 
is of a reddish while colour > it loses its lustre 
by exposure to the air ; its specific gravity is 
about 9.8 ; it is hard, but breaks with a smart 
stroke of a hammer ; it melts about 480°. In 
a strong red heat, bismurh burns w-ith a blue 
flame, and emits yellow fumes. It combines 
with oxygen and sulphur, and forms alloys 
with most of the metals. 

The weight of an atom of bismuth, may be 
derived from its oxides and sulphuret : it seems 
to be about 68 times the weight of an atom of 

Antimony. Some of the ores ot this metal 
were known to the ancients ; but the metal in- 
a pure state, has not been known more than 
300 years. Antimony has a greyish white 
colour, and considerable brilliancy ; its spe- 
cific gravity is 6.7 or 6.8 ; it is very brittle ; it 
melts about 810" Fahrenheit ; it loses its lustre 
in time by exposure to the air. Antimony 
combines with oxygen, sulphur, and phos- 
phorus ; and it forms alloys with most of the 
other metals. 

The weight of an atom of antimony, is 


determinable from its compounds with oxygen 
and sulphur, and seems to be 40 times the 
weight of hydrogen. 

Arsenic. Certain compounds of Arsenic 
were known to the ancients. It seems to 
have been known in a distinct character for 
more than a century. Arsenic has a blueish 
grey colour, and considerable brilliancy, which 
it soon loses by exposure to the air ; its specific 
gravity is stated to be 8.5 ; its fusing point has 
not been ascertained, by reason of its great 
volatility : it has been heated to 350", at which 
temperature it sublimes quickly, and exhibits 
a strong smell resembling that of garlic, which 
is characteristic of this metal. It combines 
with oxygen, forming one of the most virulent 
poisons ; also with hydrogen, sulphur, and 
phosphorus ; and it forms alloys with most of 
the metals. 

The weight of an atom of arsenic, appears 
from its compounds to be 42 times that of 

Cobalt. The ore of this metal has been 
long used to tinge glass blue ; but it was not 
till the last century that a peculiar metal was 
extracted from it. Cobalt is of a grey colour, 
inclining to red ; it has not much lustre : its 
specific gravity is about 7.8; it is brittle; it 
melts at 180" of Wedgwood ; it is attracted 


by the magnet, and is itself capable of being 
made magnetic, according to Wenzel. Co-r 
bait combines with oxygen, sulphur, and phos- 
phorus; and it forms alloys with most of the 
metals, but they are of little importance. 

The weight of an atom of cobalt cannot be 
accurately obtained from the data we have at 
present ; it is probably 50 or 60 times that of 

Manganese. The dark brown mineral 
called manganese, has been known and used 
in the glass manufactories, perhaps more than 
a century : but the meral which now goes by 
the same name, was not discovered till about 
40 years ago : in fact, it is not yet much 
known, being obtained with difficulty, and by 
a great heat. 1 he metal is of a greyish white 
colour, and considerable brilliancy : its specific 
gravity is 6.85 or 7 ; it is brittle, and melts at 
160° of Wedgwood ; when reduced to powder, 
it is attracted by the magnet, which is sup- 
posed to be owing to the presence of iron. 
Manganese attracts oxygen from the air, be- 
coming grey, brown, and finally black. It is 
capable of being combined with sulphur and 
phosphorus ; and it forms alloys with some of 
the metals, but they have not been much ex- 

The weight of an atom of manganese, as 


determined from its oxides, seems to be about 
40 times that of hydrogen. 

Chromium. This metal, united to oxygen 
so as to constitute an acid, is found in the Tcd 
lead ore of Siberia. The pure metal being 
obtained, is white inclining to yellow ; it is 
brittle, and requires a great heat to fuse it. It 
combines with oxygen. The other properties 
of this metal are not yet known. Its atom, 
perhaps, weighs about J 2 times that of hy- 

Uranium. This metal was discovered by 
Klaproth, in 1789, in a mineral found in Sax- 
onv. It is obtained with some difficulty, and 
only in small quantities ; it has, therefore, 
been examined but by few. The colour of 
uranium is iron grey ; it has considerable 
lustre ; it yields to the file ; its specific gravity 
is 8.1, according to Klaproth ; 9.0, according 
to Bucholz. Uranium unites with oxygen, and 
probably with sulphur : its alloys have not been 

The weight of an atom of this metal, is pro- 
bably about 60 times that of hydrogen. 

^Molybdenum. The ore from which this 
metal is obtained is a sulphuret, called molijb- 
dcna ; but it requires an extraordinary heat to 
reduce it ; the metal has not hitherto been 
obtained, except in small grains. It is of a 


yellowish white colour ; its specific gravity is 
7.4, according to Hielm ; but 8.6, according 
to Bucholz. It combines with oxygen, sul- 
phur, and phosphorus ; and it forms alloys 
with several of the metals. 

The atom of molybdenum, probably weighs 
about 60 times that of hydrogen. 

Tungsten. This metal is one of those recently 
discovered. It is difficultly obtained, requiring 
an excessive heat for its fusion. It is of a 
greyish white colour, and considerable bril- 
liancy J its specific gravity is 17.2 or 17.6 ; it is 
very hard, being scarcely impressed with a file. 
It combines with oxygen, sulphur, and phos- 
phorus ; and it forms alloys with other metals. 

We have not sufficient data, from which to 
determine the weight of an atom of tungsten : 
as far as we can judge from its oxides, its 
weight must be 55 times that of hydrogen, or 

Titanium. This metal has been lately dis- 
covered. It is said ro be of a dark copper 
colour ; it has much brilliancy, is brittle, and 
possesses in small scales a considerable degree 
of elasticity. It is highly infusible. It tar- 
nishes on exposure to the air ; is oxidized by 
heat, and then becomes blueish. It unites 
with phosphorus, and has been alloyed with 
iron. It detonates when thrown into red hot 


nitre. The atom of titanium probably weighs 
about 40 or 50 times that of hydrogen. 

CoLUiMBiuM. In 1802, Mr. Hatcheft dis- 
covered a new metallic acid in an ore con- 
taining iron, from America. He did not 
succeed in reducing the acid to a metal ; but, 
from the phenomena it exhibited, there was 
little room to doubt of its containing a peculiar 
metal, which he called columbium. 

Tantalium. This metal has lately been 
discovered by M. Ekeberg, a Swedish che- 
mist. A white powder is extracted from 
certain minerals, which appears to be an oxide 
of this metal. When this white oxide is 
strongly heated along with charcoal, in a cru- 
cible, a metallic button is formed, of external 
lustre, but black and void of lustre within. The 
acids again convert it into the state of a white 
oxide, which does not alter its colour when 
heated to redness. 

Cerium. The oxide of this metal is ob- 
tained from a Swedish mineral. No one has 
yet succeeded completely in reducing this ox- 
ide ; so that the properties of the metal, and 
even its existence, are yet unknown. But the 
earth or supposed oxide, is found to have pro- 
perties similar to those of other oxides. These, 
of course, belong to a future article, the me- 
tallic oxides. 

269 ) 



xN order to understand what is intended to 
be signified by binary and ternary compounds, 
&c. tlie reader is referred to page 213 and seq. 
Some persons are used to denominate all com- 
pounds, where only two elements can be dis- 
covered, binary compounds ; such, for in- 
stance, as nitrous gas, nitrous oxide, nitric 
acid, 8ic. in all of which we find only azote 
and oxygen. But it is more consistent with 
our views to restrict the term binary^ to signify 
two atoms ; ternary^ to signify three atoms, 
&c. whether those atoms be elementary or 
otherwise ; that is, whether they are the atoms 
of undecompounded bodies, as hydrogen and 
oxygen, or the atoms of compound bodies, as 
water and ammonia. 

In each of the following sections, we shall 
consider the compounds of some two of the 
elementary or undecompounded bodies ; be- 
ginning each section with the binary com- 
pounds, then proceeding to the ternary com- 


pounds, or at least to those which consist of 
three atoms, though they may be biliary in the 
sense we use the term -, and so on to the more 
complex forms. 

This chapter will comprehend all the aeri- 
form bodies that have not been considered in 
the last, several of the acids, the alkalies, the 
earths, and the metallic oxides, sulphurets, 
carburets, and phosphurets. 

In treating of these articles, I intend to 
adopt the most common names for them ; but 
it will be obvious, that if the doctrine herein 
contained be established, a renovation of the 
chemical nomenclature will in some cases be 



I . Water, 

This liquid, the most useful and abundant 
of any in nature, is now well known both by 
analytic and synthetic methods, to be a com- 
pound of the two elements, oxygen and hy- 

Canton has proved that water is in degree 
compressible. The expansive effect of heat 

WATER. 271 

on water has been already pointed out. The 
weight of a cubic foot of water is very near 
1000 ounces avoirdupoise. This fluid is com- 
monly taken as the standard for comparing the 
specific gravities of bodies, its weight being 
denoted by unity. 

Distilled water is the purest ; next to that, 
rain water ; then river water ; and, lastly, 
spring water. By purity in this place, is 
meant freedom from any foreign body in a 
state of solution ; but in regard to transpa- 
rency, and an agreeable taste, spring water 
generally excels the others. Pure water has 
the quality we call soft >• spring and other im- 
pure water has the quality we call hard. 
Every one knows the great difference of wa- 
ters in these respects ; yet it is seldom that the 
hardest spring water contains so much as T-p-^jTyth 
part of its weight of any foreign body in solu- 
tion. The substances held in solution are usu- 
ally carbonate and sulphate of lime. 

Water usually contains about 2 per cent, of 
its bulk of common air. This air is originally 
forced into it by the pressure of the atmo- 
sphere ; and can be expelled again no other 
way than by removing that pressure. 'I his 
may be done by an air-pump ; or it may in 
great part be effected by subjecting the water 
to ebullition, in which case steam takes the 


place of the incumbent air, and its orcssure is 
found inadequate to restrain the dilatation of 
the air in the water, which of course makes its 
escape. But it is difficult to expel all the air 
by either of those operations. Air expelled 
from common spring water, after losing 5 or 10 
percent, of carbonic acid, consists of 38 per 
cent, of oxygen and 62 of azote. 

Water is distinguished for entering into 
combination with other bodies. To some it 
unites in a small definite proportion, consti- 
tuting a solid compound. This is the case in 
its combination with the fixed alkalies, lime, 
and with a great number of salts ; the com- 
pounds are either dry powders or crystals. 
Such compounds have received the name of 
hydrates. But when the water is in excess, a 
different sort of combination seems to take 
place, which is called solution. In this case, 
the compound is liquid and transparent ; as 
when common salt or sugar are dissolved in 
water. When any body is thus dissolved in 
water, it may be uniformly diffused through 
any larger quantity of that liquid, and seems to 
continue so, without manifesting any tendency 
to subside, as far as is known. 

In 1781, the composition and decomposition 
of water were ascertained ; the former by 
Watt and Cavendish, and the latter by Lavoi- 

WATER. 273 

sier and Mcusnier. The first experiment on 
the composition of water on a large scale, 
was made by Monge, in 1783 ; he procured 
about -l- lb. of water, by the combustion of 
hydrogen gas, and noted the quantities of hy- 
drogen and oxygen gas which had disappeared. 
The second experiment was made by Le 
Fevre de Gineau, in 1788 ; he obtained about 
2^ lbs. of waUT in the same way. The third 
was made by Fourcroy, Vauquelin, and Se- 
guin, in 1790, in which more than a pound 
of water was obtained. The general result 
was, that 85 parts by weight of oxygen unite 
to 15 of hydrogen to form 100 parts of water. 
— Experiments to ascertain the proportion of 
the elements arising from the decomposition 
of water, were made by Le Fevre de Gineau 
and by Lavoisier, by transmitting steam 
through a red hot tube containing a quantity 
of soft iron wire ; the oxygen of the water 
combined with the iron, and the hydrogen 
was collected in gas. The same proportion, 
or 85 parts of oxygen and 1 5 of hydrogen, were 
found as in the composition. 

The Dutch chemists, Dieman andTroostwyk, 
first succeeded in decomposing water by elec- 
tricity, in 1789. The effect is now produced 
readily by galvanism. The composition of 
water is easily and elegantly shewn, by means 


of Volta's eudiometer, an instrument of the 
greatest importance in researches CQncerning 
clastic fluids. It consists of a strong gra- 
duated glass tube, into which a wire is her- 
metically sealed,' or strongly cemented -, ano- 
ther detached wire is pushed up the tube, 
nearly to meet the former, so that an electric 
spark or shock can be sent from one wire to 
the other through any portion of gas, or mix- 
ture of gases, confined by water or mercury. 
The end of the tube being immersed in a 
liquid, when an explosion takes place, no 
communication with the external air can arise ; 
so that the change produced is capable of being 

The component parts of water being clearly 
established, it becomes of importance to de- 
termine with as much precision as possible, 
the relative weights of the two elements con- 
stituting that liquid. The mean results of 
analysis and synthesis, have given 85 parts of 
oxygen and 15 of hydrogen, which are gene- 
rally adopted. In this estimate, I think, the 
quantity of hydrogen is overrated. There is 
an excellent memoir in the 53d vol. of the 
Annal. de Chemie, 1805, by Humboltd and 
Gay-Lussac, on the proportion of oxygen and 
hydrogen in water. They make it appear, 
that the quantity of aqueous vapour which 

WATER. 275 

elastic fluids usually contain, will so far influ- 
ence the weight of hydrogen gas, as to change 
the more accurate result of Fourcroy, &c. of 
85.7 oxygen and 14.3 hydrogen, to 87.4 oxy- 
gen and 12.6 hydrogen. Their reasoning ap- 
pears to me perfectly satisfactory. The re- 
lation of these two numbers is that of 7 to 1 
nearly. There is another consideration which 
seems to put this matter beyond doubt. Jn 
Volta's eudiometer, Iwo measures of hydrogen 
require just one of oxygen to saturate them. 
Now, the accurate experiments of Cavendish 
and Lavoisier, have shewn that oxygen is 
nearly 14 times the weight of hydrogen ; the 
exact coincidence of this with the conclusion 
above deduced, is a sufficient confirmation. — 
If, however, any one chooses to adopt the 
common estimate of 85 to 15, then the re- 
lation of oxygen to hydrogen will be as .^^ to 
1 ; this would require the weight of oxy- 
genous gas to be only Uptimes the weight of 

The absolute weights of oxygen and hy- 
drogen in water being determined, the relative 
weights of their atoms may be investigated. 
As only ojie compound of oxygen and hy- 
drogen is certainly known, it is agreeable to 
the 1st rule, page 214, that water should be 
concluded a binary compound, ; or, one atom 


of oxygen unites with one of hydrogen to form 
one of water. Hence, the relative weights of 
the atoms of oxygen and hydrogen are 7 to 1. 

The above conclusion is strongly corrobo- 
rated by other considerations. Whatever may 
be the proportions in which oxygen and hy- 
drogen are mixed, whether 20 measures of 
oxygen to 2 of hydrogen, or 20 of hydrogen 
to 2 of oxygen, still when an electric spark is 
passed, water is formed by the union of 2 mea- 
sures of hydrogen with 1 of oxygen, and the 
surplus gas is unchanged. Again, when wa- 
ter is decomposed by electricity, or by other 
agents, no other elements than oxygen and hy- 
drogen are obtained. Besides, all the other 
compounds into which those two elements 
enter, will in the sequel be found to support 
the same conclusion. 

After all, it must be allowed to be po'ssible 
that water may be a ternary compound. In 
this case, if two atoms of hydrogen unite to 
one of oxygen, then an atom of oxygen must 
weigh 14 times as much as one of hydrogen 3 
if two atoms of oxygen unite to one of hydro- 
gen, then an atom of oxygen must weigh 3|- 
times one of hydrogen. 


2. Fluoric Acid. 

The acid obtained from the fluor spar, which 
abounds in Derbyshire, is one of those the base 
of which has not yet been clearly ascertained ; 
but, guided partly by theoretic reasoning, and 
partly by experience, I have ventured to place 
it among the compounds of hydrogen with 
oxygen, and to rank it next to water in sim- 
plicity of constitution ; it is, as I conceive, a 
compound of two atoms of oxygen with one 
of hydrogen. 

Scheele and Priestley have distinguished 
themselves in investigating the properties of 
this acid ; and Dr. Henry and Mr. Davy have 
attempted to decompose it. The acid may be 
obtained by taking a quantity of pounded fluor 
spar (fluate of lime), putting it into a gas bottle 
with about the same weight of sulphuric acid 
undiluted, and then applying a heat, so as to 
raise the temperature to about the boiling heat 
of water. The acid is produced in the gaseous 
form, and must be received over mercury ; but 
if it is intended to condense it in water, then 
the gas, as it is generated, may be sent into a 
receiver containing some water at the bottom 5 
the water will rapidly absorb the gas, and in- 
crease in density. 


Some of the* properties of this acid are, 1. In 
the elastic state it is destructive of combustion, 
and of animal life ; it has a pungent smell, 
somewhat like muriatic acid, and not less suf- 
focating ; its specific gravity has not been ac- 
curately obtained ; but from some experiments 
I have made, it seems to be extremely heavy 
when obtained in glass vessels ; in fact, it is in 
that case a superfluate of silica : Into a clean 
dry flask, I sent a quantity of fluoric acid gas ; 
after some time, the mixture of common air 
and acid was corked, and the flask weighed : 
it had acquired 12 grains. The flask was next 
inverted in water, to see how much would be 
absorbed, and that quantity was taken for the 
acid gas. The capacity of the flask was 26 
cubic inches, containing originally 8.2 grains 
of common air; 12 cubic inches of acid gas 
had entered. According to this, if the whole 
flask had been filled with the gas, it would 
have gained 26 grains ; consequently, 26 cubic 
inches of the acid gas would weigh 34.2 
grains, and its specific gravity be 4.17 times 
that of common air. This experiment was 
repeated with a proportional result. The flask 
became partially lined with a thin, dry film 
of fluate of silica during the operation, which 
no doubt contributed something to the weight ; 
but I am convinced, from other experiments. 


that this gas, when loaden with silica, is hea- 
vier than most others. A tube, four tenths of 
an inch in diameter, and 10 inches long, being 
filled with this acid gas, and inverted for one 
minute, retained only -^V^ths of the gas ; 
whereas, with carbonic acid gas, it retained 
4^^ths J and with oxymuriatic acid gas, ^VVths. 
2. Water absorbs a very large portion of this 
gas ; but the quantity is, like as in. other si- 
milar cases, regulated by the temperature and 
pressure conjointly : at the common tempe- 
rature and pressure, I have observed 2 grains 
of water take up 200 times their bulk of the 
gas, and leave little residuum besides common 
air. It is seldom obtained in large quantities 
of this strength j when water has imbibed its 
bulk of the gas, it has a sour taste, and all the 
other characters of acids. 3. The property of 
dissolving silica (flint) is peculiar to this acidj 
when it is obtained, as usual, in glass vessels, 
it corrodes the glass, and takes up a portion of 
silica, which is held in solution in the trans- 
parent gas ; but as soon as this comes in con- 
tact with water, the silica is deposited in form 
of a white crust, namely, fluate of silica, on 
the surface of the water. 4. The gas, when 
thrown into common air, exhibits white fumes 
(like muriatic acid) ; this is owing to its com- 
bining with the steam or aqueous vapour, 


which common air always contains in a dif- 
fused state. ' 5. Fluoric acid combines with 
the alkalies, earths, and metallic oxides, form- 
ing salts denominated JIuates. 

The weight of an atom of fluoric acid may 
be investigated from the salts into which it 
enters as an integral element. Of these, the 
filiate of lime is most abundant, and best 
known. Scheele is said to have found 57 parts of 
lime, and 43 of acid and water, in fluate of lime. 
Richter finds Qb lime, and 35 acid in this salt. 
These are the only authorities I know : they 
differ materially. In order to satisfy myself, 1 
took 50 grains of finely pulverized spar, and 
having mixed with it as much, or more, strong 
sulphuric acid, the whole was exposed to a 
heat gradually increasing to redness ; the re- 
sult was, a hard dry crust of mixed sulphate 
and fluate of lime; this was pulverized, then 
weighed, and again mixed with sulphuric 
acid, and heated as before ; this process was 
repeated two or three times, or as long as any 
increase of weight was found. At last, a dry 
white powder, of 75 grains, was obtained, 
which was pure sulphate of lime. This expe- 
riment, two or three times repeated, gave al- 
ways 75 grains finally. Hence, 50 grains of 
fluate of Jime contain just as much lime as 75, 
grains of sulphate of lime: But sulphate of 


lime is formed of 34 parts acid + 23 parts lime ; 
now, if 57 : 23 : : 75 : 30 = the lime in 50 
fiuate of lime. Hence, fluate of lime consists 
of 60 lime + 40 acid, in 100 parts : a result 
which is nearly a mean between the two be- 
forementioned. Again, if 60 : 40 : : 23 : 15 
nearly, for the weight of fluoric acid which is 
found associated with 23 parts of lime ; but 23 
will be found in the sequel to represent the 
weight of an atom of lime ; therefore, 15 re- 
presents the weight of an atom of fluoric acid, 
it being assumed that fluate of lime is consti- 
tuted of one atom of acid united to one atom 
of lime. 

Before we commence the analytical investi- 
gation of this acid, it will be proper to discuss 
its relation to steam or aqueous vapour, which 
appears at present to be much misunderstood ; 
the observations equally apply to muriatic acid 
gas, and to some others, which will be no- 
ticed in their places. It is universally known, 
that common air over water contains a quantity 
of steam or vapour, some way or other com- 
bined or mixed with it, which does not im- 
pair its transparency, but which gives it -ji^-th 
of its elastic force, at the temperature of 65° ; 
the vapour too, increases and diminishes in 
force and quantity in same ratio with the tem- 
perature. Clement and Desormes have shewn, 


that this vapour is the same in quantity for at- 
mospheric air, oxygen, hydrogen, azote, and 
carbonic acid, and probably for most other 
gases. This vapour can be abstracted from the 
gases by any body possessing an attraction for 
water ; such as sulphuric acid, lime, &c. In 
short, it can be taken out, as far as is known, 
by any body tliat will take out pure steam. 
Some authors consider the vapour united to 
the air by a slight affinity ; others call it hy- 
grometrical affinity, &c. My opinion on this 
subject has already been stated, that the steam 
mixed with air diffi^rs in no respect from pure 
steam j and, consequently, is subject to the 
same laws. There are some elastic fluids, 
however, which have so strong an affinity for 
water, that they will not permit this steam 
quietly to associate with them ; these are fluo- 
ric, muriatic, sulphuric, and nitric acids. No 
sooner are these acid gases presented to any 
air containing steam, but they seize upon the 
steam ; the two united, are converted into a 
liquid ; visible fumes appear, which after play- 
ing about a while, are observed to fall down, 
or adhere to the sides of the vessel, till the gas 
no longer finding any steam present, occupies 
the volume of the vessel in a transparent state, 
free from every atom of vapour. These acid 
gases cannot exist one moment along with 


Steam ; they are no longer elastic fluids, but 
liquids ; the drops of liquid float about, and 
cause the visibility, till, like rain, they sub- 
side ; they are not reabsorbed ; for, if the sur- 
face of a glass vessel is once moistened with 
them, it remains so. Hence, it should seem 
that these acid gases, so far from obstinately 
retaining their vapour, as is commonly ima- 
gined, they cannot be induced to admit any 
vapour at all, in ordinary circumstances. This 
being clearly understood, we can now proceed 
to consider the experiments on the analysis of 
fluoric acid. 

In the Philos. Transact, for J 800, Dr. Henry 
has given us an interesting set of experiments 
on the decomposition of the muriatic acid by 
electricity : at the conclusion, he observes on 
fluoric acid — " When electrified alone, in a 
" glass tube, coated internally with wax, it 
" sustained a diminution of bulk, and there 
*' remained a portion of hydrogenous gas." 
Now, admitting the accuracy of the fact, it 
seems fair to infer, that hydrogen is a consti- 
tuent principle of fluoric acid ; and not, as he 
supposed, derived from the water it contains, 
More recently, Mr. Davy has ascertained, (see 
Philos. Transact, for 1808) that potasium burns 
in fluoric acid, and the result is fluate of pot- 
ash, and a little hydrogen gas is liberated. In 


particular, IOt grains of potasium were burned 
in 19 cubic inches of fluoric acid, 14 of which 
disappeared, fluate of potash was formed, and 
2^ cubic inches of hydrogen were evolved. 
Here it is evident, that both oxygen arid hy- 
drogen were found in the fluoric acid, and 
must have made an integral part of that acid, 
as no vapour could subsist in it \ whence it 
appears, that both oxygen and hydrogen are 
essential to fluoric acid. Moreover, it is highly 
probable that the pure acid in the 14 inches of 
gas, weighed about 6 grains, (common air be- 
ing 4^) and the oxygen necessary for \0\ po- 
tasium, would be 2 grains ; whence the acid 
entering into composition, would be about 
twice the weight of the oxygen united to the 

I shall now relate some of my own expe- 
riments on the decomposition of this acid. 

1. Fluoric acid gas may, 1 find, be kept in 
glass tubes for several hours or days, without 
any change of bulk ; it continues at the end 
absorbable by water as at first. Two suc- 
cessive trials were made, by electrifying about 
30 water grain measures of the gas. After 
two hours electrification, no change of volume 
was produced. Water was then admitted, 
which absorbed all but 4 grain measures ; to 
this 14 measures of hydrogen were added, and 


a sufficient quantity of oxygen ; the whole 
was then exploded, and a diminution of 23.3 
was observed, denoting 15,5 hydrogen. Here 
seems, then, to have been a decomposition of 
the acid, and a formation of 1.5 hydrogen. 
This was the result of the latter experiment, 
and the former was to the same effect. 

2. Fluoric acid gas, electrified along with 
hydrogen, experiences a diminution, but this 
is much greater in the hydrogen than in the 
acid. The result of one of the most careful 
experiments follows. A mixture of 20 mea- 
sures of fluoric acid, and 1 3 of hydrogen, was 
electrified for three hours uninterruptedly, by 
a dense stream of sparks ; it diminished from 
33 to 19 ; of the loss, 10 was found to be hy- 
drogen, and 4 acid. — Here the hydrogen must, 
probably, have formed water with part of the 
oxygen of the acid. 

3. Fluoric acid was mixed with oxygen, 
and electrified one hour ; a small diminution 
was observed, and the surface of the mercury 
was tarnished. 

4. Fluoric acid gas was mixed with oxymu- 
riatic acid gas : no sensible change was pro- 

Upon the whole, it appears that the weight 
of an atom of fluoric acid is about 15 times 
that of hydrogen, that it contains hydrogen 


and oxygen, and nothing besides as far as is 
certainly known. Now, as the weight of one 
atom of hydrogen, and two of oxygen, just 
make 15 times that of hydrogen, there Is great 
reason to presume that this must be the con»- 
stitution of that acid. Besides, analogy is 
strongly in favour of the conclusion ; an atom 
of the other elementary principles, azote, car- 
bone, sulphur, and phosphorus, joined to two 
atoms of oxygen, each forms a peculiar acid, 
as will be shewn in the sequel j why, then, 
should not one atom of hydrogen and two of 
oxygen, also form an acid ? 

3. Muriatic Acid. 

To obtain muriatic acid in the elastic state, 
a portion of common salt, muriate of soda, is 
put into a gas bottle, and about an equal 
weight of concentrated sulphuric acid ; by the 
application of a moderate heat to the mixture, 
a gas comes over, which may be exhibited over 
mercury ; it is muriatic acid gas. 

Some of the properties of muriatic acid gas, 
are: 1. It is an invisible elastic fluid, having 
a pungent smell j it is unfit for respiration, or 
for the support of combustion ; when mixed 
with common air, it produces a white cloud. 


which is owin^to its combination with steam, 
and the consequent formation of innumerable 
small drops of liquid muriatic acid. 2. Its 
specific gravity appears to be about 1.61 times 
that of common air, from some experiments of 
mine ; but, according to Brisson, it is 1 .43 ; and 
according. to Kirwan, 1.93 at the temperature 
of 60°, and pressure of 30 inches of mercury. 
There are two sources of error obvious in de- 
termining its specific gravity ; the one is, that 
liquid muriatic acid is apt to insinuate itself, 
if the utmost attention is not paid to have the 
mercury in the vessel dry, in which case the 
weight is found too great ; this is probably 
Kirwan's error : the other is, a quantity of 
common air may be mixed with the acid gas, 
in wliich case its weight will be too little. 
In order to find the specific gravity of this gas, 
I adopted the same method as with fluoric acid 
(see page 278). A flask containing 8.2 grains 
of common air, when partially filled with mu- 
riatic acid gas, (namely i^ths) acquired just 3 
grains ; and a like proportion in several other 
trials'; from which I find the specific gravity 
given above. 3. It possesses the characterisic 
properties of acids ; namely, that of converting 
vegetable blues to red, of uniting with al- 
kalies, &c. 4. It is rapidly and largely ab- 
sorbed by water, which takes up between four 


and five hundred times lis bulk of the gas, at 
the common temperature and pressure ; that 
is, rather less than an equal weight. This 
combination of water and muriatic acid gas, 
constitutes the common liquid muriatic acid, 
or spirit of salt of commerce ; but it is never 
of the strength indicated above. It is usually 
of a yellow colour, owing to some atoms of iron 
which it holds in solution. 

The constitution of this acid, is a question 
that has long engaged the attention of chemists. 
Thisacidseemsmoredifficultly decomposed than 
most others. Electricity, so powerful an agent 
in the composition and decomposition of other 
acids, seems to fail in this. In the Phil. Tr. for 
1800, Dr. Henry has given us the results of a 
laborious investigation on this subject. From 
these it appears that pure, dry muriatic acid 
gas, is scarcely affected by electricity. A very 
small diminution in volume, and some traces 
of hydrogenous gas, were observed, which he 
ascribes to the water or steam which the gas 
contains. But we have already remarked, 
(page 283) that muriatic acid gas naturally 
contains no steam ; or, if it contains any, it 
must be much less than other gases contain. 
It is probable, therefore, that the hydrogen 
was derived from the decomposition of part of 
the acid. This conclusion is strengthened by 


i^e recent experiments of Mr. Davy, in which 
the acid has apparently undergone a complete 
decomposition. In his Electrochemical Re- 
searches, in the Philos. Transact, for 1808, he 
observes — ' When potasium was heated in mu- 

* riatic acid gas, as dry as it could be obtained 

* by common chemical means, there was a 

* violent chemical action with ignition ; and 

* when the potasium was in sufficient quan- 

* tity, the muriatic acid gas wholly disap- 
' peared, and from one third to one fourth of 

* its volume of hydrogene was evolved, and 

* muriate of potash was formed.' Here it is 
almost certain a portion of the acid was de- 
composed ; the residuary hydrogen, and the 
oxygen required to convert the potasium into 
potash, are the only ostensible elements of the 
acid ; hence we must infer, that muriatic acid 
is a compound of oxygen and hydrogen. In 
a subsequent paper in the same volume, Mr. 
Davy informs us, that 8 grains of potasium took 
'22 cubic inches of acid gas, and gave 8 inches 
of hydrogen. This particular experiment must, 
hpwever, be incorrect in some point; or other- 
wise the general observation before made ; 
because they are inconsistent with each other. 
For, 22 cubic inches of acid gas weigh 1 1 
grains, to which adding 8 grains of potasium, 
we obtain 19 grains ; but 8 grains of potasium" 


form only 14.6 grains of muriate of potash, to 
which adding .2 grain for the 8 cubic inches 
of hydrogen, gives 14.8 instead of 19 grains. 
I would therefore adopt the general fact, 
which was confirmed by several experiments, 
and is entirely consistent ; namely, that when 
potasium in sufficient quantity is burned in mu- 
riatic acid gaSy t/te whole of the gas disap- 
pears ^ and from one third to one fourth of its 
volume of hydrogen is evolved, and muriate of 
potash formed. This is one of the most im- 
portant facts that has been ascertained, re- 
specting the constitution of muriatic acid. 
Now, the elements of muriate of potash are 
as follow : 35 grains of potasium + 7 of oxy- 
gen = 42 of potash ; and 42 potash + 22 mu- 
riatic acid = 64 grains of muriate of potash. 
Vroni this it appears, that the oxygen in mu- 
riate of potash is nearly I of the weight of the 
acid. According to this, when potasium is 
burned in muriatic acid gas, nearly -' of the 
whole weight (for the hydrogen weighs little) 
goes to the oxidizement of the potasium, and 
the remaining | unite with the potash formed. 
Jlcnce, when 22 cubic inches, or II grains 
of gas disappear, as in the particular experi- 
ment lately mentioned, 2i grains nearly must 
have been oxv2:en derived from the acid, and 
^l grains of acid joined to the potash so 


formed. But 2A grains of oxygen = 8 cubic 
inches, would require 16 inches of hydrogen 
to form water : it is evident, then, that water 
was not the source of the oxygen ; for, if it 
had, there must have been twice the quantity 
of hydrogen evolved. Mr. Davy has ascer- 
tained another fact, exactly similar to the ge- 
neral one just stated; namely, that when char- 
coal is galvanized in muriatic acid gas, mu- 
riate of mercury is formed, and hydrogen, 
amounting to 4- of the volume of the gas is 
evolved. He infers from this, that water is 
present to form oxide enough to saturate the 
acid ; but, setting aside the inference I have 
drawn, that no water can be present with 
muriatic acid gas, the oxygen required to form 
the oxide in this case as well as the former, 
if derived from water, would evolve at least 
twice as much hydrogen. For, the relation of 
the oxygen in the oxide to the acid in the 
muriate, is proved by the fact, to be the same 
in the two cases. 

Mt. Davy has, indeed, endeavoured to ob- 
viate any objection that may be made, as to 
the source of the oxygen in these experiments ; 
he has found that nearly the same weight of 
muriate of mercury is formed, by precipi- 
tating a mercurial solution by a given volume 
of muriatic acid gas, as by burning potasiuni 


in the same quantity of gas, and then trans- 
ferring the acid to mercury : he observes, 
' there was no notable difference in the results.' 
The inference must, I conceive, be erroneous; 
100 cubic inches of muriatic acid gas, united 
to potash, must give more muriate of potash, 
than if potasium was burned in the same gas ; 
the weights of the materials necessarily require 
it ; unless it be found that the two muriates are 
not the same salt. 

From all the muriates, or salts, into which 
the muriatic acid enters, it appears (as will be 
shewn when these salts are considered) that the 
weight of an atom of muriatic acid is 22 times 
that of hydrogen. Very soon after this deter- 
mination, it occurred to me that hydrogen was 
probably the base of the acid ; if so, an atom 
of the acid must consist of 1 atom of hydrogen 
and 3 atoms of oxygen, as the weights of these 
just make up 22. In 1807 this idea was an- 
nounced, and a suitable figurative represen- 
tation of the atom was given, in the Chemical 
Lectures at Edinburgh and Glasgow ; but this 
constitution of the acid was hypothetical, till 
these experiments of Mr. Davy seem to put it 
past doubt. The application of the theory to 
the experiments is as follows : on the suppo- 
sition that the specific gravity of muriatic aCid 
gas is 1.G7, it will be found that 12 measures 


of the acid contain 11 aieasures of hydrogen, 
if liberated, and about 164 measures of oxy- 
gen ; then if ^th of the acid be decomposed, 
nearly 3 measures of hydrogen will be libe- 
rated, and 4 -f- measures of oxygen, and the 
atoms of this oxygen will apply, 1 to 1, to the 
atoms of potasium, and furnish potash for the 
remaining iths of the acid, (because 1 atom of 
acid contains 3 of oxygen). The very same 
explanation will apply to the formation of mu- 
riate of mercury. Here the hydrogen will be 
rather less than ^th of the volume of the acid 
gas ; but if we adopt Kirwan's specific gravity 
of muriatic acid, 1.93, then the hydrogen 
evolved will be between 4 and ^th of the vo- 
lume of acid gas. 

Hence we conclude that an atom of muriatic 
acid gas consists of 1 atom of hydrogen and 3 
of oxygen, or 1 atom of water and 2 of oxy- 
gen, and its weight = 22. Moreover, the dia- 
meter of the acid atom will be found (page 226) 
= 1.07, that of hydrogen being 1 ; or 12 mea- 
sures of acid contain as many atoms as 1 1 mea- 
sures of hydrogen, or as 5 ^ of oxygen. 

My own experiments on muriatic acid gas 
have not been productive of important results. 
I sent 1000 small shocks of electricity through 
30 measures of gas ; there was a diminution of 


1 measure, and on letting up water the whole 
was absorbed, except one measure, which 
appeared to be hydrogen. I sent 700 shocks 
through a mixture of muriatic acid gas and 
hydrogen ; there was no change. A mixture 
of muriatic acid gas and sulphuretted hydrogen 
being electrified, hydrogen was evolved, and 
sulphur deposited, but no change of volume. 
It was evident the sulphuretted hydrogen only 
was decomposed. When a mixture of oxygen 
and hydrogen is fired along with muriatic acid 
gas, water is formed, and it instantly absorbs 
nearly its weight of acid gas. From these and 
such like unsuccessful attempts to decompose 
the muriatic acid, the importance of Mr. Davy's 
experiments is manifest. 

The relation of muriatic acid to water must 
now be considered. It has been stated that 
water at the common temperature and pressure, 
absorbs 400 or more times its bulk of the acid 
gas ; that is, rather less than its own weight. 
Now, 3 atoms of water weigh 24, and 1 atom of 
the acid gas weighs 22 j it seems probable, then, 
that the strongest liquid acid that can well be 
exhibited, is a compound of 1 atom of acid 
and 3 of water, or contains about 48 per cent, 
acid. It is seldom sold of more than half this 
strength. Mr. Kirwan's table of the strength 



of muriatic acid of different specific gravities is 
very nearly correct ; which, with some little 
addition and modification, is as follows : 

Table of the quantity of real acid in 100 
parts of liquid muriatic acid, at the tempe- 
rature 60°. 


Acid per 

Acid per 



cent, by 

cent, by 



cid. Water. 



1+ 1 

1+ 2 
1+ 3 






1+ 4 


1+ 5 


1+ 6 


J+ 7 


1+ 8 





I-h 9 





1+ 10 





1+ 11 





1-h 12 





1+ 13 










1+ 15 





1 + 20 





I + 25 




228 « 

1+ 30 





1+ 40 





1+ 50 


5 39 



1 -i- 100 





1 4- 200 





The first column shews the number of atoms 
of acid and warer which are found combined 
in liquid acids of the different specific gravities ; 
the second contains the acids per cent, by 
weight ; that is, 100 grains of the liquid acid 


contain so many grains of pure acid ; the third 
contains the grains of acid in 100 water grain 
measures j this is convenient in practice to 
prevent the trouble of weighing the acid ; the 
fourth contains the specific gravity of the liquid 
acid J and the fifth contains the temperature 
at which acids of the various strengths boil. 
This last is entirely new, I apprehend ; it 
shews a remarkable gradation of temperature : 
the strong acid boils at a moderate heat ; as 
the acid weakens, the boiling temperature 
rises till it gets to 232° ; after which it gra- 
dually d'-ops again to 212°. When an acid 
below 12 per cent, is boiled, it loses part of 
its quantity, but the remainder, T find, is con- 
centrated ; on the other hand, an acid stronger 
than 12 per cent, is rendered more dilute by 
boiling. It aopears from a paper of Dr. R. 
Percival in the 4th vol. of the Irish Transac- 
tions, that in the ordinary process of manu- 
facturing the muriatic acid, the middle pro- 
duct is usually of the strength which boils at 
the maximum temperature ; but the first and 
last products are much stronger. The reasons 
for these facts will probably be found in the 
gradation of temperature in the above column. 


3. Oxifnmriatic Acid. 

The highly interesting compound, now de- 
nominated oxymuriatic acid, was discovered 
by Scheele, in 1774. It may be procured by 
applying a moderate heat to a mixture of mu- 
riatic acid and oxide of manganese or red 
lead ; a yellowish coloured gas ascends, which 
may be received over water ; it is oxymuriatic 
acid gas. But this gas, which is largely ob- 
tained for the purposes of bleaching, is usually 
got from a mixture of equal weights of com- 
mon salt (muriate of soda), oxide of manga- 
nese, and a dilute sulphuric acid of the strength 
1.4; a heat at least equal to that of boiling 
water, seems required for the expulsion of the 
whole of the acid gas. Some of its properties 
are : 

1. It has a pungent and suffocating smell, 
exceeding most other gases in these respects, 
and it is highly deleterious. Its specific gra- 
vity I find to be 2.34, that of common air be- 
ing 1. Or, 100 cubic inches of it, at com- 
mon pressure and temperature, weigh 72^^ 

2. Oxymuriatic acid gas is absorbed by 
water, but in a very small degree compared 
with muriatic acid gas. I find that at the 


temperature of 60° and common pressure of 
pure gas, water takes up about twice its bulk 
of the gas. If the gas be diluted with air, 
then much less is absorbed, but the quantity 
is not proportionate to the abstract pressure of 
the gas, as is the case with those gases men- 
tioned at page 201. Thus, if the pressure of 
oxymuriatic acid gas be ^th of atmospheric 
pressure, water will be found to take up.^ds 
of its bulk, which is more than twice the quan- 
tity it ought to take by the rule of proportion. 
Hence it is evident, that the absorption of this 
gas by water, is partly of a mechanical and 
partly of a chemical nature. 

3. Water impregnated with the gas is called 
liquid oxymuriatic acid. It has the same 
odour as the gas, and an astringent, not acid, 
taste. "When exposed to the light of the sun, 
the liquid acid is gradually decomposed, as 
was first observed bv Berthollet, into its ele- 
ments, muriatic acid and oxygenous gas j the 
former remains combined with the water, and 
the latter assumes the gaseous form. Neither 
light nor heat has been found to decompose the 
acid gas 

4. This acid, in the gaseous state or combined 
with water, has a singular effect on colouring 
matter. Instead of converting vegetable blue 
into red, as other acids do, it abstracts colours 


in general from bodies, leaving them white or 
colourless. The oxygen combines with the 
colouring principle, and the. muriatic acid re- 
maining dissolves the compound. Hence the 
use of this acid in bleachinof. 

5. Combustible bodies burn in oxymuriatic 
acid gas more quickly than in common air, 
and the combustion is attended with several 
remarkable phenomena. Some bodies spon- 
taneously take fire in this gas. All the metals 
are oxidized by this acid, and afterwards dis- 
solved, forming salts denominated viiiriates. 
The combustible gases, mixed in due propor- 
tions with this acid gas, are either burned im- 
mediately, as sulphurous acid, sulphuretted 
hydrogen, nitrous gas, &c. or the mixture is 
capable of being exploded by an electric spark, 
as hydrogen, carburetted hydrogen, &c. These 
facts shew that the oxygen which combines 
with muriatic acid to form oxvmuriatic, is ea- 
sily abstracted again to enter into almost any 
other combination. 

6. Oxymuriatic acid seems to combine rea- 
dily with the fixed alkalis and the earths when 
dissolved in water ; but it decomposes ammo- 
nia. It is remarkable, however, that few, if 
any, neutralized dry salts are to be obtained. 
When the saturated solutions are evaporated 
and crystallized, two distinct salts are chiefly 


obtained ; the one a simple itiuriate, and the 
other a hyperoxygenized muriate,- in which an 
acid with an enormous quantity of oxygen is 
found, and is hence called hyperoxipmiriatic 

7. One very remarkable property of oxymu- 
riatic acid has recently occurred to me in a 
cour^f- of experiments upon it. Cruickshanks 
had found that if hydrogen and oxymuriatic 
acid gases were mixed together, and kept in a 
well stopped bottle for 24 hours, when the 
stopper was withdrawn under water, the gases 
disappeared, and water took their place. Be- 
ing desirous to ascertain the time more defi- 
nitely, I made the mixture in a narrow eudio- 
meter, and left it to stand over water ; in about 
three quarters of an hour the greater part of 
the mixture had disappeared. In the next 
experiment, the gases, after being put toge- 
ther, seemed to have no effect for one or two 
minutes, when suddenly the mixture began to 
diminish with rapidity, like one of common air 
and nitrous gas, except that there were no red 
fumes. The diminution went on, till in two 
or three minutes nearly the whole had dis- 
appeared. On repeating the experiment a 
^e.\v hours afterwards no such diminution was 
observed. I recollected that the sun had shone 
upon the instrument in the former one j it was 


again placed in the direct rays of the sun, and 
the diminution was rapid as before. Upon 
repeating the experiment with sundry varia- 
tions, it was confirmed, that Light is the occa- 
sion of this rapid combustion of hydrogen in 
oxymuriatic acid gas ; that the more powerful 
the light, the more rapid is the diminution of 
the mixture ; and that if the eudiometer be 
covered by an opake body, the mixture will 
scarcely be affected with any diminution for a 
day, and will not completely disappear in two 
or three weeks. Moreover, when the dimi- 
nution is going on with speed, if the hand, or 
any opake body, is interposed to cut off the solar 
light, the diminution is instantly suspended. 
These observations equally apply to mixtures 
of carbiiretted hydrogen and carbonic oxide 
with the acid gas, except that the former de- 
posits some charcoal. Carbonic acid, water, 
and muriatic acid, are the results. — These facts 
were ascertained in June 1809. In the ensu- 
ing month, 1 found that upon mixing hydro- 
gen and oxymuriatic acid in a strong phial 
capable of containing COO grains of water, 
and exposing the mixture to the solar rays, an 
explosion almost instantly took place with a 
loud report, just as if it had received an electric 
spark. If the stopper was well closed, a va- 
cuum nearly was formed, which was instantly 


filled with water when the stopper was drawn 
out under water j but it generally happened 
that the stopper was expelled with violence. 

It remains now to point out the constitution 
of this acid. AH experience shews, that it is 
a compound of muriatic acid and oxygen ; but 
the exact proportion has not hitherto been 
ascertained. Berthollet, who investigated the 
subject by impregnating water with the acid 
gas, and then exposing it to the solar rays till 
the oxygen was liberated, found it to consist 
of 89 parts of muriatic acid, and 1 1 of oxy- 
gen, by weight. Whether all the oxygen is 
liberated in this way is more than doubtful ; 
the quantity of oxygen is certainly much under- 
rated. Chenevix makes 84 muriatic acid and 
16 oxygen to constitute this acid ; he too has 
the oxygen too low ; probably because he es- 
timated all the salt formed by this acid to be 
simple muriate, or hyperoxymuriate ; but there 
is no doubt that oxymuriate does exist in the 
mixture, because it possesses the property of 
bleaching. Of all the authors I have seen, 
Cruickshank comes the nearest to the truth ; 
he says, 2 measures of hydrogen require 2.3 
measures of oxymuriatic acid to saturate them ; 
and it is known that they require 1 of oxygen ; 
hence he infers, that 2.3 measures of this acid 
gas contain 1 measure of oxygen. From this 


it may be inferred, that 100 measures of the 
acid gas would afford 43.5 measures of oxy- 
genous gas, and a certain unknown measure 
of muriatic acid (not 56.5, as Dr. Thomson has 
inferred)'. Chenevix remarks, that Cruick- 
shank's gas was obtained from hyperoxymuriate 
of potash, and that ' the substance he ob- 

* tained was, in fact, not oxygenized muriatic 

* acid gas, but a mixture of that gas with hy- 
' peroxygenized muriatic acid.* Dr. Thomson 
observes, that * when water, impregnated with 

* oxymuriatic acid gas, obtained by Cruick- 

* shank's method, is mixed with liquid ammo- 

* nia, scarcely any gas is extricated. The two 

* bodies combine and form a salt.' I do not 
know what reasons these two authors may have 
had for making these remarks ; but, accord- 
ing to my experience, they are entirely with- 
out foundation. The acid gas obtained from 
a mixture of sulphuric acid, muriate of soda, 
and manganese, or from muriatic acid and 
manganese, or from hyperoxymuriate of pot- 
ash and muriatic acid, are all precisely the 
same, .vhether we consider their action upon 
the combustible gases, upon liquid or aeriform 
ammonia, or their absorbability by water. 
There is indeed one small difference, but it 
does not seem productive of any material ef- 
fect ; the gases obtained by the two former 


methods always deposit some brown oxide of 
manganese when treated with ammonia, but 
that obtained by the last deposits none. The 
action of muriatic acid on hyperoxymuriate of 
potash, evidently consists in detaching the 
superfluous oxygen from the compound, and 
not the hypcroxymuriatic acid particle from the 
particle of potash. 

As the oxymurlatic acid is of great and in- 
creasing importance in a theoretical as well as 
practical point of view, I have spent much 
time in endeavouring to ascertain the pro- 
portion of its elements, and have, I think, 
succeeded ; at least, 1 am pretty well satisfied 
myself as to its constitution : the methods I have 
taken are both synthetical and analytical, but I 
chiefly rely upon the latter. 

1. I filled a eudiometer with dry mercury, 
and sent up 13 water grain measures of muri- 
atic acid gas, to which were added 9 measures 
of oxygenous gas of 77 per cent, purity, which 
consequently consisted of 7 oxygen and 2 azote. 
The instrument had platina wires. About 
1300 small electric shocks were passed through 
the mixture of gases ; a gradual diminution 
ensued ; the mercury became foul, the same 
as when oxymuriatic acid is in contact with it. 
The 22 measures were reduced to 4, which 
were not diminished by v^'ashing. To these 4 


measures, 20 hydrogen and 20 common air 
were added, and the mixture being exploded, 
the diminution was 15 measures, correspond- 
ing to 5 oxygen ; but the common air con- 
tained only 4 oxygen ; therefore, 1 measure of 
oxygen must have been in the residuary gas, 
and probably 1 of azote was originally in the 
muriatic acid. Here then, it seems, 12 mea- 
sures of muriatic acid united to 6 measures of 
oxygen to form oxymuriatic acid. — If we cal- 
culate from the specific gravities of the three 
elastic fluids, it will appear that 12 measures 
of muriatic acid gas, + 6 measures of oxygen 
gas, ought to make II measures of oxymu- 
riatic acid gas. This result is nearly right ; 
but the process is too laborious to be often re- 
peated, especially as the object can be ob- 
tained much more easily and elegantly by the 
analytic method. 

■2. Oxymuriatic acid gas and hydrogen, 
mixed together over water, explode with an 
electric spark, much like a mixture of com- 
mon air and hydrogen. Cruickshank mixed 3 
measures of hydrogen with 4 of the acid, and 
exploded them over mercury : in this case, 
there was a residuum of acid gas. He then 
mixed 4 measures with 4, and after the ex- 
plosion found a residuum of hydrogen. From 
these experiments, he infers, that 3 measures 


of hydrogen require 3^ of the acid to saturate 
them. I have found the results a little differ- 
ent ; but the error is not much, and is what 
might be expected. Whether we treat oxy- 
muriatic acid over mercury or water, we are 
sure to lose some of it ; and unless the loss can 
be estimated and allowed for, we are apt to 
overrate the acid required. Before the action 
of light on this mixture was discovered, I used 
to mix known quantities of the two gases to- 
gether, in a graduated eudiometer of Volta, 
over water ; and, after letting the mixture 
stand a few minutes, in order to c complete 
diffusion, I passed a spark through, but no- 
ticed the moment before at what degree the 
mixture stood ; in this way, when there is an 
excess of hydrogen, the results are accurate ; 
the total diminution can be found, and the re- 
siduary gas can be analyzed to find the hy- 
drogen left, and the common air (if any), 
which is extremely apt to be found in a greater 
or less degree, in all oxymuriatic acid obtained 
over water. By frequent careful trials, I found 
that a measure of hydrogen required as near 
as possible an equal measure of the acid to sa- 
turate it. But since the effect of solar light 
was discovered, I have operated in a more 
simple and elegant manner ; and the results 
appear rather more uniform and accurate. I 


take a graduated tube, capable of containing 
200 measures of gas. 1 fill this with water, 
and transfer into it 100 measures of hydrogen 
of known purity ; to this a quantity of acid 
gas is added, so as to fill the tube nearly. 
The finger is then applied to the end of the 
tube, and it is instantly transferred to ajar of 
mercury. The whole is then taken, and ex- 
posed to the sun, (if not shining too power- 
fully, in which case an explosion may be ap- 
prehended) or to the strongest light that can 
be obtained ; when, after remaining two or 
three minutes without exhibiting any change, 
the water, and afterwards the mercury, ascend 
the tube with increasing and then diminishing 
velocity, till they nearly reach the top. The 
residuary gas may then be examined, and the 
quantity of hydrogen, acid and common air, 
ascertained. The quantity of water in the 
tube becomes visible as the mercury ascends, 
and is useful to prevent the action of the acid 
on the" mercury. The water must l>e sub- 
tracted from the capacity of the tube, to find 
the volume of gases employed, from which 
taking the hydrogen, there remains the 
acid, &c. 

From the mean of five experiments executed 
as above, I am induced to conclude, that 100 
measures of hydrogen require 94 measures of 


oxymuriatic acid gas to convert them into 
water. In every one of the experiments, the 
acid was less than the hydrogen. 

The above experiments are highly amusing 
in a day of clouds and gleams ; the presence 
of the direct solar light instantly gives the mo- 
tion of the mercury a stimulus, and it as 
quickly abates when a cloud incervenes. The 
surface of the mercury in the tube always 
becomes fine sky blue during the process ; and 
so does liquid ammonia that has been used to 
decompose oxymuriatic acid ; I do not know 
what is the reason in either case. 

From the results above, it appears that 100 
measures of oxymuriatic acid gas must consist 
of 53 measures of oxygen, united to a certain 
portion of muriatic acid gas. Now, ICO cubic 
inches of oxymuriatic acid gas weigh 72 or 73 
grains, and 53 inches of oxygen weigh about 
18 grains, which is rather less than ^th of the 
above. Hence, if the atom of muriatic acid 
weigh 22, that of oxymuriatic acid must weigh 
29 ; and thus we obtain the constitution of this 
last acid. An atom of it consists of one of 
muriatic acid and one of oxygen.. united ; the 
former weighs 22, the latter 7, together mak- 
ing 29 ; or about 76 muriatic acid, and 24 
oxygen, per cent. Thus, it appears, that the 
former experiments on the specific gravities of 

hYperoxymuriatic acid. 309 

those fluids, corroborate the recent ones on 
their constitution. If the constitution of mu- 
riatic acid be rightly determined, then oxy- 
muriatic acid must consist of 1 atom of hy- 
drogen and 4 of oxygen. At all events, 1 
atom of muriatic acid must combine with 1 of 
oxygen to form I of oxymuriatic acid. The 
diameter of the elastic atom of this gas is 
nearly the same as hydrogen, and may there- 
fore be denoted by 1, but it is rather less ; and 
the number of atoms in a given volume of this 
gas is to the number in the same volume of 
hydrogen, as 106 to 100 nearly. It appears, 
then, that the atoms of oxymuriatic acid are 
rather more dense than those of muriatic acid, 
or than those of hydrogen. 

5. Hyperoxymurialic Acid. 

The existence of a compound denominated 
hyperoxymuriatic acid, has been clearly shewn 
in a state of combination ; but it has not, and 
perhaps can not, be exhibited in a separate, 
elastic, or even liquid form, probably on ac- 
count of the great weight and number of its 
elementary parts. It is clearly a compound of 
muriatic acid and an enormous quantity of oxy- 
gen. It is obtained in combination with the 


alkalies and earths, by sending a stream of oxy- 
muriatic acid gas into solutions of these ele- 
ments, or of their carbonates in water. The acid 
combines with the alkali j but in process of 
time, as the solution becomes concentrated, a 
change takes place in the acid ; one atom of 
oxymuriatic acid seizes upon an atom of oxy- 
gen from each of its neighbouring particles, 
and reduces them to ordinary muriatic acid ; in 
this state it forms with an atom of alkali an 
hyperoxymuriate, whilst the other atoms of 
acid form muriates. It seems that the oxymu- 
riates are difficultly attainable ; because, as 
their solutions are concentrated, they are so 
apt to be resolved and compounded again, as 

BerthoHet first pointed out the peculiarity 
of this acid : but iis nature and properties were 
more fully discussed by Hoyle in 1797, and by 
Chenevix in 1802. These authors made their 
principal experiments on hyperoxymuriate of 
potash ; they nearly agree as to the constitu- 
tion of the salt, but differ in some of the cir- 
cumstances of its production. It yields by heat 
about 2 or 3 per cent, of water, about 38 per 
cent, of oxygen, and 59 or (50 of a salt unal- 
terable by heat, which Chenevix considers as 
simple muriate j but Hoyle says it exhibits 
traces of oxvmuriatic acid bv sulphuric acid. 


The acid in 59 muriate is nearly 20. Hence, 
20 muriatic acid added to 38 oxygen by 
weight, constitute 58 of hyperoxy muriatic acid : 
or, as Chenevix states it, 65 oxygen + 35 mu- 
riatic acid = 100 hyperoxymuriatic acid. This 
I judge to be very nearly true. Now, if 35 
muriatic acid require 65 oxygen, 22 will take 
41 ; but 22 is the weight of an atom of muri- 
atic acid, and 41 or 42 is the weight of 6 atoms 
of bxygen ; hence the constitution of hyper- 
oxymuriatic acid is determined. An atom of 
it consists of 1 atom of muriatic acid + 6 atoms 
of oxygen, or of 1 atom of oxymuriatic acid 4- 
5 atoms of oxygen ; and its weight is repre- 
sented by 64. We may now see what takes 
place in the formation of hyperoxymuriates. 
One atom of oxymuriatic acid deprives 5 sur- 
rounding atoms, each of an atom of oxygen ; 
an atom of hyperoxymuriate thus necessarily 
produces 5 atoms of simple muriate. Sup- 
posing the salts from potash, their weights may 
be found thus : An atom of potash weighs 42, 
one of hyperoxymuriatic acid weighs 64, to- 
gether = 106. Five atoms of muriate of pot- 
ash = 320; the sum of both = 426. Now, if 
426 : 106 : : 100 : 25 nearly. Hence, in the 
formation of hyperoxymuriate of potash, if the 
whole potash is formed into muriate and hy- 
peroxymuriate, there must be 75 of the former 


and 25 of the latter. Hojrle does not inform 
us on this head ; Chenevix found 84 of the 
former and 1 6 of the latter. Here then is some 
obscurity. The fact, I believe, is, that there 
is always a greater or less portion of real oxy- 
muriate of potash amongst the salts formed, or 
in the mass which Chenevix calls the entire 
salt. Oxymuriatic acid precipitates silver from 
nitrate as well as muriatic ; and as this was the 
test, it is evident Chenevix must have con- 
founded a quantity of oxymurrate of potash 
with the muriate. The quantity may even be 
ascertained. For, if 25 : 75 : : 16 : 48. In 
100 of Chenevix's entire salt, there were then 
16 by peroxy muriate, 48 muriate, and the rest 
or 36 must have been oxymuriate. Hoyle's 
experiments confirm this conclusion j for, he 
observes that the remaining muriate (after the 
hyperoxyrauriate was abstracted) was consi- 
derably oxygenized, since with the addition of 
acids it became a powerful destroyer of vege- 
table colours. This could not be the case with 
a muriate, nor even a mixture of muriate and 
hyperoxymuriate. Besides, it is well known 
that the oxymuriate of potash (or oxymuriatic 
acid absorbed by potash) was largely used for 
the purpose of bleacliing ; now if the acid had 
immediately resolved itself into muriatic and 


hyperoxymuriatic, it would have been of no 
use for that purpose. 

Hyperoxmuriatic acid must then be constir 
tuted of 1 atom of muriatic acid and 6 of oxy- 
gen ; but as the former is probably composed 
of 1 atom of hydrogen and 3 of oxygen, we 
have 1 atom of hydrogen + 9 of oxygen for 
the constitution of an atom of the first men- 
tioned acid ; or it consists of 1^^ hydrogen + 
98|- of oxygen per cent, by weight. It is no 
wonder, then, if this acid readily part with its 
oxygen, and be apt to explode when treated 
"with combustible bodies ; nor if it refuse to 
form an elastic fluid of such unwieldy par- 

Note on Fluoric and Muriatic Acids. 

Since the foregoing articles on fluoric and 
muriatic acid were printed oflf, I have seen the 
Journal de Physique, for January 1809, in 
which is an abstract of an highly interesting 
Memoir on the Fluoric and Muriatic Acids, 
by Gay-Lussac and Thenard. Their obser- 
vations, supported by facts, are remarkably in 
unison with those I have suggested They 
find that when fluoric acid gas is admitted to 
any gas, and produces fumes, the gas is dimi- 


nished, but only a small quantity ; that when 
no fumes appear, no diminution takes place j 
they hence conclude, that this acid gas is au 
excellent test of the presence of hygrometric 
water [steam] in gases ; and observe that all 
gases contain such, except fluoric, muriatic, 
and probably ammoniacal. Berthollet, jun. 
has proved the last mentioned gas to contain 
no combined water ; and Gay-Lussac and 
Thenard suspect it contains none hygrometri- 
cally ; but some experiments of Dr. Henry con- 
vince me that it does ; and I think its not 
fuming when mixed with common air is a 
proof of it. — They observe, that when water 
is saturated with fluoric acid gas, it is limpid, 
smoking, and extremely caustic ; that heat 
expels about one fifth of the acid, and the re- 
mainder becomes fixt, resembling concentrated 
sulphuric acid, and requiring a high tempera- 
ture to boil it. They query from this fact, 
whether sulphuric and nitric acid are not na- 
turally gasiform, and owe their liquidity to 
the water combined with them. They exposed 
a drop of water to 60 cubic inches of fluoric 
acid gas j the drop, instead of evaporating, 
was increased in volume by the absorption of 
the acid ; and hence they conclude, that flu- 
oric acid gas is also free from combined water j 
the conclusion is extended to ammoniacal 


gas, but not to muriatic acid gas. I wonder 
at their exception with regard to muriatic 
acid, as every one knows it presents the same 
phenomena when a drop of water is admitted ; 
that is, the drop is increased by the condensed 
acid, and suffers no evaporation. They allude, 
however, to the experiments of Henry and 
Berthollet, in which water was supposed to be 
found in a state of intimate union with this 
acid gas; and they mention some of their own, 
in which one fourth of the weight of the gas 
was found to be water. This conclusion of 
muriatic acid gas being the only gas that con- 
tains water combined with it, they consider as 
striking ; and seem inclined to consider water 
as a constituent of the acid, but that the oxygen 
and hydrogen are not in the state of water. 

Gay-Lussac and Thenard found that fluoric 
acid gas, detached from fluate of lime by bo- 
racic acid, does not dissolve silica, on account 
of the boracic acid which it holds in solution. 
Another remarkable fact was, that fluate of 
lime, distilled with sulphuric acid in leaden 
vessels, does not give the fluoric acid in an 
elastic, but in a liquid form. — They observe, 
as Davy had done, that in burning potasium 
in siliceous fluoric acid gas, some hydrogen is 
given out, amounting successively to about 
one third of what would be given out by water. 


They seem to think that the acid is de- 
composed in this case : but they have not 
advanced any opinion, that either fluoric or 
muriatic acid gas consists entirely of hydrogen 
and oxygen. 



The compounds of oxygen with azote, hi- 
therto discovered, are five ; they may be dis- 
tinguished by the following names ; nitrous 
gas, nitric acid, nitrous oxide, nitrous acid, 
and oxynitric acid. In treating of these, it 
has been usual to begin with that which con- 
tains the least oxygen, (nitrous oxide) and to 
take the others in order as they contain more 
oxygen. Our plan requires a different prin- 
ciple of arrangement ; namely, to begin with 
that which is most simple, or which consists 
of the smallest number of elementary particles, 
which is commonly a binary compound, and 
then to proceed to the ternary and other higher 
compounds. According to this principle, it 
becomes necessary to ascertain, if possible, 
whether any of the above, and which of them, 
is a binary compound. As far as the specific 


gravities of the two simple gases are indicative 
of the weights of their atoms, we should con- 
clude that an atom of azote is to one of oxy- 
gen as 6 to 7 nearly ; the relative weights of 
ammonia and water also give countenance to 
such a ratio. But the best criterion is derived 
from a comparison of the specific gravities of 
the compound gases themselves. Nitrous gas 
has the least specific gravity of any of them ; 
this indicates it to be a . binary compound ; 
nitrous oxide and nitrous acid are both much 
heavier; this indicates them to be ternary com- 
pounds ; and the latter being heavier than the 
former, indicates that oxygen is heavier than 
azote, as oxygen is known to abound most in 
the latter. Let us now see how far the facts 
already known v/ill corroborate these ob- 

According to Cavendish and Davy, who 
are the best authorities we yet have in regard 
•to these compounds, they are constituted as 
under • 



Sp. gr. 
iS'itrousgas 1.102 

Nitr. oxide 1.6 1 i 
Nitric acid 2AU 

5 — 

constitution bv \vcight. 
+0.G azote -|- 13.4- oxy. 






2/;. 3 

+ 55.8 — 
H-57.7 — 
-I- 3(i..5 — 

+ .',if) 




4- 74.(3 


6. 1 :7 




5.9:7 X 

5.4:7 X^ /- 




The above table is principally taken from 
Davy's Researches: where two or more results 
are given under one article, they are derived 
from different modes of analysis. In the third 
column are given the ratios of the weights of 
azote and oxygen in each compound, derived 
from the preceding column, and reduced to 
the determined weight of an atom of oxygen, 
7. This table corroborates the theoretic views 
above stated most remarkably. The weight 
of an atom of azote appears to be between 5.4 
and 6.1 : and it is worthy of notice, that the 
theory does not differ more from the experi- 
ments than they differ from one another ; or, 
in other words, the mean weight of an atom 
of azote derived from the above experiments 
would equally accommodate the theory and 
the experiments. The mean is 5.6y to which 
all the others might be reduced. We should 
then have an atom of nitrous gas to weigh 
12.6, consisting of 1 atom of azote and 1 of 


oxygen ; an atom of niirous oxide to weigh 
18.2, consisting of 2 atoms of azote and 1 of 
oxvgen ; and an atom of nitrous acid to weigh 
19.6, consisting of 1 atom of azote and 2 of 
oxygen. Nor has the weight of an atom of 
oxygen any influence on the theory of these 
compounds ; for, it is obvious that if oxygen 
were taken 3, or 10, or any other number, 
still the ratios of azote to oxygen in the com- 
pounds would continue the same ; the only 
difference would be, that the weight of an 
atom of azote would rise or fall in proportion 
as that of oxygen. 

I have been solicitous to exhibit this view of 
the compounds of azote and oxygen, as de- 
rived from the experience of others, rather 
than from my own ; because, not having had 
any views at all similar to mine, the authors 
could not have favoured them by deducing the 
above results, if they had not been contormablc 
to actual observation. 

I come now to make some observations on 
the results contained in the preceding tables, 
and to state those of my own, which have been 
obtained with labour and assiduity. 

I believe the above mean weight of an 
atom of azote, 5.6, is too large ; and that the 
true mean is but little above 5; perhaps 5.1, 
or 5.2. — I do not mean by this observation to 


insinuate that the results in the above table 
are derived from inaccurate experiments. In 
the course of my investigations, I have had to 
repeat the experiments ot many ; but have 
found no results to which my ovvqi in general 
approximated so nearly as to those of Mr. 
Davy in his Researches. As knowledge ad- 
vances, however, greater precision is attainable 
from the same facts. As for Mr. Cavendish's 
important experiments, they were intended to 
shew what elements constitute nitric acid, ra- 
ther than the proportion of them ; and they 
were made at too early a period of pneumatic 
chemistry to obtain precision. 

The first line of the table contains the pro- 
portions of azote and oxygen in nitrous gas, as 
determined by the combustion of pyrophorus, 
Mr. Davy justly considers this as least entitled 
to confidence. The second and third were 
obtained from the combustion of charcoal in 
nitrous gas. The second is grounded upon 
the oxygen found in the carbonic acid. By 
making the calculation of this from more re- 
cently determined proportions of charcoal and 
oxygen, I reduce the azote to 5.4. The third 
is derived from the azote left after combustion. 
Mr. Davy finds 15.4 measures of nitrous gas 
yield 7.4 of azote ; or 100 measures of nitrous 
gas yield 48 measures of azotic gas. 


Dr. Priestley was the first to observe that 
the electric spark diminishes nitrous gas, and 
finally leaves azotic gas ; he states the reduction 
,to be to one fourth of the volume. I have 
several times repeated this experiment with all 
possible attention to accuracy ; the exact quan^ 
tity of azote in the nitrous gas was previously 
determined by sulphate of iron, and was com- 
monly 2 per cent. ; the quantity of jO or 100 
water grain measures of the gas was put into a 
narrow eudiometer tube over water, furnished 
with platina wires ; the electrification was for 
one or two hours, and uninterruptedly conti- 
nued till no further diminution was observable. 
To the residuary gas a small portion of com- 
mon air was added, and no diminution found. 
In this way, from 100 measures of pure nitrous 
gas there are obtained at a mean 24 measures 
of azo^c gas ; or, which is the same thing, 
102 measures of the 98 per cent, gas leave a 
residuum of 26 azote. The deviation was 
never more than 1 ()er cent, from the above j 
that is, from 100 measures of pure nitrous gas 
I never obtained more than 25 measures of 
azote, nor less than 23. I believe, therefore, 
that 24 measures may be safely relied upon as 
an accurate approximation. 

This experiment, taken in conjunction with 
the last mentioned one of Mr. Davy, is of 

3'22 oxYonv with azote. 

great importance. It not only shews the con- 
stitution of nitrous gas, but that of nitric acid 
also. It appears, that by electrification ex- 
actly one half of the azotic gas is liberated ; 
and its oxygen joins to the ofher half to form 
nitric acid. The immediate effect of the 
electric shock is to separate the atoms of azote 
and oxygen, which by their junction form 
nitrous gas ; the moment the oxygen is libe- 
rated, it is seized by another atom of nitrous 
gas, and the two united form an atom of 
nitric acid which escapes into the water. In 
other words, ICX) measures of nitrous gas con- 
tain 48 of azote j by electrification, 24 mea- 
sures of azote are liberated, and the other C4 
measures acquire the oxygen lost by the for- 
mer, and become nitric acid, which are ab- 
sorbed by the water. 

A repetition of Mr. Cavendish's experiments 
\\\\\ be found to confirm the above conclusion. 
I have in three or four instances undertaken 
experiments of the same nature, and with like 
results ; but as these are of a laborious kind, 
it is not so convenient to execute them. One 
of these was more particularly an object of at- 
tention, and I shall relate it in the detail. A 
quantity of pure oxygenous gas was diluted 
with common air by degrees till the mixture 
contained 29 measures per cent, of azote, that 


being presumed to be nearly the due proportion 
to form nitric acid. The test was, exploding 
it with hydrogen, and taking -^ of the dimi- 
nution for oxygen. A portion of distilled 
water was impregnated with this mixture of 
gases, and put into a eudiomet-jr furnished 
with platina wires. Into this, 50 measures of 
the mixed gases were put, and the electrifi- 
cation commenced ; after several hours elec- 
trification, it was reduced to 20 measures ; it 
continued there all night without any change, 
the operation was resumed next day, and 
the gas was reduced to 13 measures. These 
were found to be 34 azote + 9^ oxygen ; or 
27 azote + 73 oxygen per cent. Hence it 
was evident, that 29 measures per cent, of 
azote were too small ; by calculation from the 
above data, it will be found that 30 measures 
of azote unite to 70 of oxygen to form nitric 
acid. This gives 27 of azote by weight, and 
73 of oxygen in nitric acid ; which nearly 
agrees with the mean of Cavendish. From 
this, the weight of an atom of azote comes out 
5.15. — By the experiment on nitrous gas, sup- 
posing its specific gravity 1.10, and that of 
azote .966, the weight of an atom of azote 
comes out 5.1. 

With respect to nitrous oxide, I think Mr. 
Davy's calculations scarcely do justice to his 


experiments. The first line shews the results 
derived from the combustion of hydrogen in 
nitrous oxide. From several experiments, 
Mr. Davy selects one in which 39 measures of 
nitrous oxide and 40 of hydrogen were fired 
together, and seemed just to saturate each 
other, leaving a residuum of 41 azote ; but 
this residuum must have contained a few atoms 
of azote originally mixed with the oxide and 
the hydrogen, and may therefore be supposed 
to be overrated. If we suppose 39 oxide to 
contain 40 azote, it will reduce the weight of 
an atom of azote from 6,1 to 5.6. In my own 
experience, equal volumes of nitrous oxide 
and hydrogen, saturate each other, and the 
volume of azote left is equal to one of the 
other two, making the due allowance for im- 
purities. This would imply that a measure of 
azote + half a measure of oxygen, should, 
when combined, constitute a measure of ni- 
trous oxide ; but the united weights are about 
5 per cent, too little, according to the specific 
gravity of the oxide given above. I appre- 
hend the oxygen this way is underrated, owing 
perhaps to the formation of an unperceived 
quantity of nitric acid. In the second line, 
we have the proportions of azote and oxygen 
in nitrous oxide, derived from the combustion 
of both phosphuretted hydrogen and charcoal 


in the oxide. By the former, nitrous oxide 
gave an equal volume of azote ; by the latter, 
21 measures of oxide produced 21.5 measures 
of azote, and 11.5 measures of carbonic acid. 
Now, if we suppose that a measure of nitrous 
oxide contains an equal volume of azotic gas 
weighing .966, and the rest of the weight, 
.(548 to be oxygen, the proportion will be 60 
azote + 40 oxygen per cent, by weight. Fur- 
ther, it is now known that 11.5 measures of 
carbonic acid contain 11.5 measures of oxy- 
gen ; hence 21 measures of nitrous oxide must 
contain 11.5 measures of oxygen ; say 20 mea- 
sures of oxide, because 9,0 being used in all, 
and 9 pure being abstracted from the residuum, 
the remainder 21 must have contained the im- 
purities in all the 30 measures, which could 
scarcely be less than 1. This gives as before, 
60 azote + 40 oxygen by weight per cent, in 
nitrous oxide. The third line gives the results 
obtained from the combustion of sulphuretted 
hydrogen ; here Mr, Davy found 35 measures 
of nitrous oxide saturate 20 measures of sul- 
phuretted hydrogen, and leave a residuum of 
35^ measures of azote : This seems again to 
shew that the azote is equal in volume to the 
oxide, and consequently will give as before, 
60 azote + 40 oxygen, by weight ; and the 


weight of ail atom of azote will be accordingly 
found = 5.25. 

It is' remarkable, that in the combustion of 
hydrogen in nitrous oxide, the oxygen (as esti- 
mated by the loss of hydrogen) is usually found 
below par ; and it is the same with the azote 
in the combustion of olefiant gas, as Mr. Davy 
has remarked ^ I have found it so likewise 
with carburetted hydrogen or coal gas. I ap- 
prehend when azote disappears, it is from the 
formation of ammonia. 

Besides the three compounds of azote and 
oxygen already considered, there are at least 
two more. One is called Jii I rous 2ic\d ; it is a 
compound of nitric acid and nitrous gas. The 
other I call oxynitric acid ; it is a compound 
of nitric acid and oxygen. Priestley disco- 
vered the fact that nitric acid absorbs nitrous 
gas very Jargely, and thereby becomes more 
volatile. He found that 1?0 ounce measures 
of nitrous gas over water disappeared in a day 
or two, when a phial containing 96 water 
grain measures of strong nitric acid was in- 
closed with the gas. The colour of the acid 
as it absorbs nitrous gas is gradually changed 
from pale yellow to orange, green, and finally 
blue green. Mr. Davy has used his endeavours 
to find the quantity of nitrou;. gas which nilric 


acid absorbs ; he estimates the blue green acid 
of 1.475 sp. gr. to contain 84.6 nitric acid, 
7.4 water, and 8 nitrous gas, by weight ; and 
he concludes that dihite acids absorb less ni- 
trous gas in proportion than concentrated 
acids. This subject shall be presently consi- 

Priestley discovered that nitrous gas entered 
into combination Vvith oxygen upon the mix- 
ture of the tv.'o gases. In this way it is easy 
to saturate one of the gases with" the other ; 
but it unfortunately happens that two or three 
distinct compounds are usually formed, and 
the proportion of one compound to another 
varies according to the circumstances of the 
mixture. By the constitution of nitric acid 
above determined, it follows that 10 measures 
of oxygen will require 18 measures of nitrous 
gas to convert them into nitric acid. But the 
mixture may be so managed as that 10 of oxy- 
gen shall take either 13 or 36 measures, or any 
intermediate number. As the facts relating 
to this matter have not been distinctly stated 
by any author 1 have seen, I shall subjoin the 
results of mv own experience. 

1, When 2 measures of nitrous gas arc put 
to 1 measure of oxygen, in a tube one third of 
an inch in diameter, and 5 inches in length, 
and as soon as the diminution is apparently 


ceased, which will be half a minute, ihe resi- 
duary gas is transferred into another tube, it 
will be found that 1 measure of oxygen and 1.8 
of nitrous gas have disappeared ; the mixture 
is to be made over water. 

2. When 4 measures of oxygen are put to 
1.3 of nitrous s:as in a tube two tenths of an 
inch in diameter, and 10 inches long, so as to 
fill it ; it will be found that 1 measure of oxy- 
gen will combine with 1.3 of nitrous gas, in 4 
or 5 minutes. 

3. When I measure of oxygen and 5 of ni- 
trous gas are mixed together, so as to form a 
thin stratum of air, not more than ^th of an 
inch in depth (as in a common tumbler) j it 
will be found that the oxygen will take from 
3 to 3^ measures of nitrous gas in a moment, 
and without any agitation. If equal measures 
are mixed, then 1 oxygen takes about 2.2 

4. When water has been made to imbibe a 
given portion of oxygenous gas, and is after-^ 
wards agitated in nitrous gas, the quantity of 
nitrous gas absorbed will always be more than 
exhausted water would take, by a quantity 
equal to 3.4 or 3.6 times the bulk of the oxy- 
genous gas. And, vice versa^ when water 
has imbibed a portion of nitrous gas, and is 
then agitated with oxygenous gas, the quantity 


absorbed wHl be greater than exbausted'water 
would take, by z portion which bears to the 
nitrous the ratio of 1 to 3.6. 

These facts are of a nature easily to be ascer- 
tained, and I have no doubt will be found near 
approximations to the truth, by those who may 
repeat them. They are curious and singular ; 
as we have few other examples where two 
gases form a real chemical union in such va- 
ried proportions. If the gases be not mixed 
precisely as above in a]l the circumstances, the 
results will not be the same. But in all the 
variations I have observed, I have not found 
oxygen to be saturated with less than 1.3, nor 
with more than 3.6 measures of nitrous gas. 
It is obvious that the presence of water, and 
the shortness of the column of the mixed gases, 
both contribute to the great expenditure of 
nitrous gas ; the latter probably from its suf- 
fering the union to take place instantaneously. 
On the other hand, a narrow tube makes the 
operation more slow, and removes the point 
of union far from the surface of the water ; 
these circumstances seem to increase the quan- 
tity of oxygen entering into combination. 

What then are we to conceive of this com- 
pound of oxygen and azote, in which 1 mea- 
sure of oxygen sometimes combines with 1.3 
of nitrous gas, and sometimes with 3.6, and 


according to circumstances takes any intci- 
mediate portion ? Are there indefinite grada- 
tions in the compound ? I cannot conceive 
this ; neither do the facts at all require it. All 
the products that need be admitted lo explain 
the facts are three. It has been shewn that 
1 rncasure ot oxygen requires ].8 of nitrous 
gas to form nitric acid, according to the results 
derived from the electrification of nitrous gas • 
and the conclusion is corroborated by other 
facts. It appears from the above observations. 
3 and 4, that oxygen is found sometimes to 
combine with 3.6 times its bulk of nitrous gas, 
and that this is the maximum ; but it is just 
twice the quantity requisite to form nitric 
acid ; it is evident, therefore, that a compound 
is formed in which there are twice as many 
atoms of nitrous gas as are neccssaiy to form 
nitric acid. This then may be called vitrnus 
acid ; and the elementary atoms consist of 1 
of oxygen and 2 of nitrous gas, united by che- 
mical afnnity. If the other extreme, or the 
minimum quantity of nitrous gas to which oxy- 
gen had united, had been .9, or half what is 
found in nitric acid, then this would have 
shewn the union of 2 atoms of oxygen with 1 
of nitrous gas, and the compound might be 
called oxi/uifric acid. Now, though it does 
not appear that we are able as yet to form 



this compound exclusively, yet it is highly 
probable that it exists, and that it is always 
formed along with niiric acid, and perhaps 
even with nitrous acid, when the oxygen con- 
sumed is more than 1 measure for 1.8 of nitrous 
gas. AVhen 1 measure of oxygen unites with 
1.8 of nitrous gas, as mentioned in the first 
observation, I conceive it is not purely nitric 
acid that is formed, but a mixture of all the 
three acids, in such proportions that the ni- 
trous and oxynitric balance each other, and in 
the sequel, when combined with water, these 
two become, by their interchange of principles, 
nitric acid. 

"We shall now proceed to remark more par- 
ticularly on the different compounds of azote 
and oxygen : but it may not be amiss to state 
here in a table their constitution, as far as 
appears from the preceding views and ob- 

Nitrous gas 
Nitrous oxide 
jSitric acid 
Oxynitric acid 
x^itious acid 

100 parts by 
Wl. off Atoms ofl u't. contain 
azote, uxv 
42.1 +37^9 

'20.1 4-7 3.. S 

fliiatoinl azote, ox. 

i2.1 = J-fl 

17.2 = 2-1-1 

19. 1 = 1+2 
2ti.l =; 1 4-3 

31.2 =z 2 4-3 

100 parts by 
nieas. contain 
azote. OX}'?. 
48 -f- 30.6 
UO.l + 3S 3 

.•>0 : 7(^* 
19.5 -I-S0.5 22. 1 : 77,9 
:j2.7 4-G7.3'3(i 2 : 63 8 

* The specific gravitie.> of the ihicc last not being accu- 
rately determined, we can only give the latios of the mea- 
sures, and nut the absoluLe quatitities of azoLe and oxygen 
in 100 measures. 


I. N 'droits Gas. 

Nitrous gas is formed by pouring dilute 
nitric acid upon many of the metals ; it should 
be received over water. The best mode of 
procuring it is to put a few small pieces or 
filings of copper into a gas bottlcj and pour 
nitric acid of the specific gravity 1.2 or 1.3 on 
to them ; the gas comes over in a state of purity 
(except so far as it is diluted with atmospheric 
air) and without the application of heat. The 
common explanation of ihis process is, that a 
part of the nitric acid is decomposed into the 
elements nitrous gas and oxygen ; its oxy- 
gen unites to the metal to form an oxide, 
which the rest of the acid dissolves. Upon a 
more particular examination of the phenomena, 
I find, that csiimaiiiig the quantity of real 
acid by Kirwan's table, ^ part of the acid is 
decomposed to furnish oxygen to the metal, 
and to yield nitrous gas, ^ unites to the me- 
tallic oxide, and the remaining 4 seizes the 
nitrous gas, and forms nitrous acid ; but in the 
degree of condensation of the acid, it is unable 
to hold more than -f or ^ of it, and the rest is 
therefore evolved. For example, 200 grain 
measures of nitric acid of 1.32 strength, di- 
luted with 100 water, dissolved 50 grains of 


copper, and yielded 44 cubic inches of nitrous 
gas =15 grains. Now, 200 measures of the 
acid contained 102 grains of real acid ; and 50 
of copper require 35 of nitric acid, which is 
nearly 4- of 102 j every atom of copper takes 
two atoms of oxygen to form the oxide, and 
this oxide takes two atoms of nitric acid to 
form the nitrate of copper (as will be shewn in 
the sequel) ; whence it appears that whatever 
quantity of acid is employed to oxidize the 
copper, an equal quantity is required to unite 
to the oxide ; the quantity of nitrous gas given 
out should therefore have been 22 grains, but 
it was only 15 : it seems, then, that 7 grains 
of nitrous gas combined with the remaining 
acid to form" 7iz/ro7/5' acid, part of which was 
probably volatilized by the heat excited in the 

Nitrous gas, according to Kirwan, has the 
specific gravity 1.19 ; according to Davy 
1.102 ; this last is the neaiest approximation 
to truth, as far as my experience goes. Its ul- 
timate particle weighs nearly 12.1 of hydro- 
gen ; the diameter of it in an elastic state is 
.958, that of hydrogen being 1 ; if a measure 
of hydrogen contain 1000 atoms, the same 
measure of nitrous gas will contam 1136 
atoms. This gas is highly deleterious when 
inspired in a dilute state; if pure, it is in- 


stantly fatal. It extinguishes combustion in 
general ; but pyroj^horus spontaneously takes 
fire in it ; and phosphorus and charcoal in an 
ignited state burn in it, and produce a decom- 
position. Pure water, (that is, water free from 
all air) I find, absorbs about ^^th of its bulk 
of nitrous gas ; but only -^^th of it can be ex- 
pelled again by other gases : it should seem, 
then, that a small portion of the gas actually 
combines with the water, while the greater 
part is, like most other gases, mechanically 
retained by external pressure. 

Nitrous gas, as has been observed, is decom- 
posed by electricity : one half of the azote is 
liberated, and the other half unites with the 
evolved oxygen, and forms nitric acid. Ac- 
cording to Davy's analysis by charcoal, nitrous 
gas is constituted of 2.2 azote, and 5 oxygen 
by weight ; or 42 azote, and 58 oxygen per 
cent, nearly ; which is the same as I obtain 
by electricity and other means. If completely 
decomposed, 100 measures tvould be expanded 
to lO'kG, of which 48 would be azote, and 
56.6 oxygen. 

Dr. Henry has recently discovered that ni- 
trous gas is decomposed by ammoniacal gas i 
the two gases are mixed over mercury in. 
Volta's eudiometer, and an electric spark is 
found sufficient to explode them. V/hen an 


excess of nitrous gas is used, the products are, 
azotic gas and water with a small portion of 
nitric acid j when an excess of ammonia is 
used, then azotic gas, water, and hydrogen 
are produced. When ammoniacal gas is sent 
through a tube, containing manganese red hot, 
Dr. Milner found that nitrous gas was formed. 
These facts exhibit remarkable instances of 
the decomposition and Composition of nitrous 

The degree of purity of nitrous gas is easily 
and accuratelv ascertained, bv means of a 
strong solution of certain salts of iron, parti- 
cularly the common sulphate or green cop- 
peras. A measure of the gas is put into a nar- 
row tube, and the end of it dipped in the 
solution ; as soon as a small poition of the 
liquid has entered the tube, a finger is applied 
to the end, and the liquid is agitated ; the 
tube is again immersed in the liquid, and the 
linger withdrawn, when a portion of the liquid 
enters : the process is repeated till no more 
gas is absorbed. What remains is usually 
azotic gas. The absorption is rapid, and the 
operation completed in a minute. This fact 
was first observed by Dr. Priestley. Wishing 
to know the nature of this combination more 
minutely, I procured a solution of green sul- 
phate, such that 6 grain measures contained 


1 grain of the salt ; its specific gravity was 
1,081 ; this was agitated with iron filings, to 
reduce any of the red sulphate that might be 
in the solution, which is known not to absorb 
the gas, into green sulphate. A eudiometer 
was filled with mercury, except one measure, 
which was filled with the liquid solution ; the 
tube was then inverted over mercury, and ni- 
trous gas sent up to the solution, which was 
afterwards agitated. It was repeatedly found 
that 1 measure of the solution absorbed 6 mea- 
sures of the gas, and was then saturated. Con- 
sequently 1500 grain measures of the solution 
would have taken 9000 grain measures of the 
gas ; but 1500 of the solution contained 250 
of salt, of which |th was iron, as is well 
known ; and 9000 grain measures of the gas 
weigh 12 grains : Here, then, 50 grains of 
iron united to 12 grains of nitrous gas. Now, 
the weight of an atom of iron is 50 (page 258), 
and that of nitrous ?as is 12. It therefore fol- 
lows, that in the combination of green sul- 
phate of iron with nitrous gas, each atom of 
iron unites with an atom of the gas, agreeably 
to the general law of chemical union. 

Nitrous gas is still used in eudiometry to 
determine the quantity of oxygenous gas in 
any mixture ; and on account of the ease and 
elegance of its application, and the quickness 


with which it attaches that gas, it will always 
be used. It has been found, however, that 
the simple mixture of the two gases is not 
enough to discover the proportion of oxygen, 
by reason of the different compounds that are 
formed. The object may be effectually ob- 
tained, by using an excess of nitrous gas of a 
known strength, and then abstracting the sur- 
plus by means of sulphate of iron. Some 
authors prefer a solution of green sulphate of 
iron saturated with nitrous gas ; the oxygenous 
gas is agitated in a portion of the solution, and 
the residuary gas is washed with a solution ot 
the sulphate, unimprcgnated with nitrous gas. 
But the quantity of oxygen in certain mixtures 
is ascertained with equal or greater precision, 
by firing it with hydrogen in Volta's eudio- 
meter, and taking -l of the diminution for 
oxygen ; or by agitating the gas in a small 
portion of sulphuret of lime, which abstracts 
the oxygen. 

When nitrous gas is mixed with oxymu- 
riatic acid gas over water, an instantaneous 
diminution of volume takes place. I was in 
expectation that this would convert the nitrous 
gas into pure nitric acid, and consequently 
the quantity of oxygen necessary would be 
ascertainable this way ; but the two gaseSj 
like oxygen and nitrous gas, combine in va- 


rious proportions, according as one or other is 
in excess. Sometimes 3 measures of nitrous 
are saturated with 2 of the acid, and some- 
times w'th 4 measures. When green sulphate 
of iron is saturated with a known portion of 
nitrous gas, and the solution is afterwards agi- 
tated with oxygen, the absorption is somewhat 
slow, (like that with sulphuret of lime) and 
the quantity taken up is equal in bulk to the 
nitrous gas. The liquid, from a dark red or 
black, becomes of a bright yellowish red, the 
oxide of iron being changed from the green to 
the red during the process. 

It has been made appear, that by electricity 
one half of the atoms of nitrous gas are decom- 
posed, in order to oxygenize the other half; 
in like manner, in certain cases, ont^ lialfoi 
the atoms of nitrous gas are decomposed to 
azotize the other half. This is shewn by the 
experiments of Priestley, but much more ac- 
curately by those of Davy. The alkaline sul- 
phites, muriate of tin, and dry sulphures, con- 
vert nitrous gas into nitrous oxide. According 
to Davy, 16 cubic inches of nitrous gas were 
converted into 7.8 of nitrous oxide by sulphite 
of potash ; that is, 100 measures gave 48.75 : 
he also found, that muriate of tin and dry sul- 
phures changed 100 measures of nitrous gas 
into 48 of nitrous oxide. These bodies have 



an affinity for oxygen ; and the moment they 
take an atom of oxygen from one of nitrous 
gas, the atpm of azote joins to another of ni- 
trous gas, and forms one of nitrous oxide. In 
this way, all the azote remains in the nitrous 
oxide, and just one half of the oxygen. By 
making the calculation from the preceding 
table, (page 331) and from the known specific 
gravities of these gases, it appears that 100 
measures of nitrous gas should make 48.5 mea- 
sures of nitrous oxide, and allow 28.3 measures 
of oxygen to combine with the bodies intro- 
duced. It is very remarkable that these nu- 
merical relations should have so long escaped 

Sulphuretted hydrogen and moistened iron 
filings also convert nitrous gas into nitrous 
oxide : but some ammonia is produced at the 
expence of the azote, and consequently less 
nitrous oxide : Davy finds about 42 or 44 
per cent. 

'J. Nih'ous Oxide. 

The gas now denominated nitrous oxide, 
was discovered, and several of its properties 
pointed out, by Priestley : he called it dcphlo- 
^'sticated nitrous gas. The Dutch chemists 


published an essay on the subject in the Journal 
de Physique for 1793, in which the consti- 
tution and properties of the gas were more 
fully investigated. In 1800, Mr. Davy pub- 
lished his Researches, containing a much more 
complete and accurate developement of the 
nature of this gas, than had previously been 
given, as well as of the other compounds of 
azote and oxygen, and several other collateral 

Kitrous oxide gas may be obtained from a 
salt called nitrate of ammonia, being a com- 
pound of nitric acid, ammonia and water. 
The salt is put into a gas bottle, and heat ap- 
plied, which first fuses the salt, about 300" ; 
by continuing the heat, the fluid salt boils, 
and is decomposed about 400°, emitting nitrous 
oxide gas and steam, into which the whole of 
the salt is principally resolved. The gas may 
be received either over water or mercury. 

The constitution of the salt, nitrate of am- 
monia, according to Davy, is when crystal- 
lized, 18.4 ammonia, and 81.6 acid and wa- 
ter : Now, if we suppose an atom of ammonia 
to be constituted of one of azote, 5.1, and one 
of hydrogen, 1, as will be shewn hereafter, 
and that an atom of the nitrate is composed of 
1 atom of each of the elements, ammonia, 
nitric acid and water, (see plate 4, fig. 36) j 


we shall have, 6.1 + 19.1 + 8 = 33.2 for the 
weight of an atom of the salt. This gives 
18.4 ammonia, and 81.6 acid and water, ex- 
actly agreeing with the experimental results of 
Davy. The decomposition of an atom of the 
salt will be found to give one atom of nitrous 
oxide, weighing 17,2, and two atoms of wa- 
ter, weighing 16. AV^hence, 100 grains of 
the salt should be resolved by heat into 51.8 
grains of nitrous oxide, and 48.2 grains of 
water. Mr. Davy decomposed 100 parts of a 
dried nitrate, that is, one which had lost 8 per 
cent, of its water of crystallization, and ob- 
tained 54.4 nitrous oxide, 4.3 nitric acid, and 
41.3 water. Here, as might be expected, the 
nitrous oxide exceeds, and the water falls 
short of the calculation, but as nearly as pos- 
sible in the due proportion. Thus it appears, 
that whether we consider the genesis of ni- 
trous oxide from the nitrate of ammonia, or 
from nitrous gas (page 338), still its consti- 
tution must be 2 atoms of azote and 1 of 

The specific gravity of this gas is 1 .614 ; the 
weight of its atom 17.2 of hydrogen j the dia- 
meter in an elastic state (to hydrogen l) is 
,947 ; if a measure of hydrogen contain 1000 
atoms, one of nitrous oxide will contain 1176 
Most combustible bodies burn in nitrous oxide 


more vigorously than in common air ; it is 
unfit for respiration, but does not so immedi- 
ately prove fatal as Dr. Priestley and the Dutch 
chemists concluded. Mr. Davy found that it 
may be respired for two or three minutes ; and 
that it generally produces sensations analogous 
to those of intcji^ication. It is absorbed by 
water to the amount of about 80 per cent, ac 
cording to n)y recent ttials. Davy makes it 
only 54 per cent., but he was not aware that 
the quantity is increased in proportion to the 
purity of the residuary gas. Dr. Henry finds 
from 78 to 86 per cent. This gas of course 
expels other gases from water, and is itself 
driven off unchanged by heat. It is a re- 
markable fact, that water should take so 
nearly, and yet not exactly, its bulk of this 

Nitrous oxide, by long electrification, loses 
about 10 per cent, of its bulk ; some nitric 
acid is formed, and a mixture of azote and 
oxygen is found in the residuum ; but no satis- 
factory decomposition is obtained this way. 

All the combustible gases, mixed with ni- 
trous oxide, explode by an electric spark. 

Nitrous oxide can be made to combine with 
the fixed alkalies ; but the nature of the com- 
pounds has not been much examined. 


3. Nitric Acid. 

Nitric acid, formerly distinguished by the 
names of aqua fortis, and spirit of nitre, has 
been known for three or four centuries. It is 
now usually procured by distilling a mixture 
of nitrate of potash (saltpetre or nitre) and sul- 
phuric acid. Two parts of the salt by weight, 
and one of concentrated acid,* are to be 
mixed in a glass retort ; heat is applied, the 
mixture becomes liquid, and soon exhibits the 
appearance of ebullition, when a yellowish 
liquid drops from the retort into a glass re- 
ceiver. It is nitric acid, one of the most 
active and corrosive of all the acids. When 
thus obtained, it is usually pure enough for 
the purposes of the arts ; but it mostly con- 
tains both sulphuric and muriatic acid : the 
former is derived from the acid employed be- 
ing in part distilled, espeoially if an excess of 
it be used and the heat be great ; the latter is 

* Authors differ greatly as to the proportion of salt and 
acid : some say 3 salt to 1 of acid : others say nearly equal 
weights; but 1 acid to 2 salt is that which wij] nearly sa- 
turate the base, and must therefore be right, unless an ex- 
cess of sulphuric acid be expedient to displace the iiitrif, 
which does not appear. 


derived from the nitre, which usually contains 
some muriates mixed with it. To obtain the 
acid pure, the nitre should be repeatedly dis- 
solved in warm water, and crystallized, taking 
out the first formed crystals for use ; and the 
acid, when obtained, should be treated with 
nitrate of barytes to precipitate the sulphuric 
acid, and nitrate of silver to precipitate the 
muriatic acid. 

The theory of this process is well under- 
stood : nitrate of potash is a compound of 
nitric acid and potash -, sulphuric acid has a 
stronger affinity for potash than nitric ; it 
therefore displaces the nitric, which with the 
water of the sulphuric acid and that of the nitre, 
is distilled by the heat, and the compound of 
acid and water constitutes the liquid nitric 
acid above. Near the end of the process, the 
heat is advanced to 500° and upwards, and the 
acid is partly decomposed ; some oxygen is 
given out, and nitrous gas, which combines 
with the acid, and forms nitrous acid vapour. 
This acid becomes mixed with the nitric, and 
renders it more fuming and volatile. The ni- 
trous acid may be driven from the liquid nitric 
by heat, and then the last becomes less volatile, 
and colourless like water. 

The specific gravity of the liquid nitric acid 
thus obtained, is usually from 1.4 to l.n : Bv 


fusing the nitre previously, and boiling the 
sulphuric acid till its temperature was 600°, I 
obtained a quantity of acid of 1.52. Byre- 
distilling with a moderate heat, it may be 
obtained of 1.55, and even as high as 1.62, 
according to Proust (Journal de Physique, 
1799). The strength of the acid, that is, the 
quantity of real acid in a given weight of the 
liquid, increases in some proportion with the 
specific gravity, as will presently be shewn. 

Some of the more remarkable properties o£ 
the liquid nitric acid follow : 1. It emits white 
vapour when exposed to the atmosphere, ow- 
ing to its combination with steam or aqueous 
vapour : this is rendered more evident in the 
distillation of nitric acid ; if the elastic vapour 
of the acid is escaping from the receiver, it 
exhibits a white cloud when breathed upon. 
2. It is sour to the taste, when diluted with 
water. 3. It corrodes animal and vegetable 
substances, and stains them yellow. 4. It 
combines with water, and, when concentrated, 
attracts it from the atmosphere j heat is pro- 
duced, and a small increase of density. With 
snow it produces, a great degree of cold, and 
instant liquefaction. 5. It is said to be de- 
composed by the solar light, giving out oxy- 
gen, and becoming orange coloured. 6. It 
inflames several combustibles, such as very dry 


charcoal, essential oils, &c. 7. When dis- 
tilled over sul[)bur, it converts the sulphur 
into sulphuric acid. 8. It oxidizes the metals, 
as has been observed, and gives out nitrous 
gas. 9. When the vapour of nitric acid is 
passed through a red hot earthen tube, the 
acid is decomposed into oxygen and azote. 
The same decomposition is effected by heating 
nitre red hot in an iron or earthenware retort. 
10. It unites to the alkalies, earths, and me- 
tallic oxides, forming salts denominated ni- 

One of the most important considerations 
relative to nitric acid is the determination of 
the quantity of real acid in a watery solution 
of a given specific gravity. This subject has 
encased the attention of several eminent che- 
mists, particularly Kirwan, Davy, and Ber- 
thollet. Their results are widely different. 
For instance ; in an acid of 1.298 sp. gravity, 
Kirwan says the real acid is 3(3? per cent. 
Davy says 48, and Berthollet 32 or 33. (See 
Journal de Physique, March 1807;.* My 
experience in regard to this particular has 

* Berthollet, by mistake, makes Davy represent the 
acid iu question to contain 5'V per cent, of acid ; but it is 
the water which he says is 54- per cent, and the acid 4o, 
when the sp. gravity is 1.283 ; so that the difTerencr, great 
as it is^ is not quite so enonnous. 


been considerable, and I shall now state it 

Nitric acid has been stated, on the authority 
of Bergman, to boil at 248°. This is true, if it 
relate to acid of the strength 1.42 ; but ta 
acids of no other strength ; in fact, it fs the 
highest possible boiling point of the liquid 
acid : but if the acid be stronger or weaker, 
then the farther it deviates from 1.42, the less 
is the temperature at which it boils. The 
weakest possible acid must evidently boil at 
SIZ''; but the point at which the strongest 
acid boils has not been determined ; it will be 
found, in all probability, little above the com- 
mon temperature of the atmosphere : an acid 
of 1.52, I find, boils about 180 or 185^ 
Proust's acid of 1.G2 would probably boil 
about 100% or about the same degree as elher. 
The results of my experience will be noted 
more particularly in the following table. Be- 
sides this variable temperature of ebullition, 
there is another concomitant circumstance, 
which has been hinted at by others : In the 
Paris Memoirs for 1781, Lassone and Cor- 
nette had ascertained that when weak nitric 
acid is boiled or distilled, the weakest portion 
comes over first ; but when the acid is con- 
centrated, the strongest portion conies over 
first: In the Irish Transactions, vol. 4, Dr. R. 


Percival has noticed some results in the distil- 
lation of nitre; 2 lbs. of nitre and 1 of concen- 
trated sulphuric acid were mixed and distilled j 
the products were received in 3 portions ; the 
first was of the strength 1.494; the second, 
1.485; the third, 1.442: Proust, in the Jour- 
nal de Physique, 1799, relates that he obtained 
an acid 1.52 ; this being again distilled, gave 
for the first product 1.51 ; for the second, 1.51, 
nearly colourless, which he expected indicated 
a superior specific gravity ; but what surprised 
him more, was to find the residue colourless, 
and 1.47. This residue was distilled ; the 
first portion was 1.49, and the rest 1.44. In 
another instance an acid 1.55 was obtained; 
this redistilled gave, first 1.G2, the second 1.53, 
and the residue was 1.49. — From all these 
facts, it appeared to me reasonable to conclude 
that an acid of some one strength, and only 
one, was incapable of any change of strength 
by distillation ; or was of such a nature, that 
the distilled part and the residue were always 
of the same strength and specific gravity. The 
actual strength of this acid was a desirable at- 
tainment ; for such an acid evidently marks a 
nice adjustment of affinities between the acid 
and water ; or a kind of mutual saturation of 
the two. By repeated experiments I find this 
acid to be of the specific gravity 1.42; it is 


remarkable also that this strength is that which 
has the boiling temperature a maximum, or 
1^48°. Any acid of inferior strength, being 
distilled, the weakest part comes over first j 
and, vice versa, with one of superior strength. 
For instances, by distilling part of an acid of 
1.30, I found an acid of 1.25 in the receiver : 
again, 530 measures of acid, 1.43 were sub- 
jected to distillation ; 173 measures were drawn 
over of 1.433, and 354 of 1.427 were left in 
the retort: again, by boiling an acid of 1.35 
for some time, it became 1.39 ; and another 
of 1.48 became 1.46 : in short, the continued 
boiling of any acid, weak or strong, makes it 
approach more and more to the density 1.42, 
and to the temperature 248". 

With respect to the quantity of real acid in 
a solution of given speciHc gravity, I find it 
thus : Agreeably to the experience of Kirwan, 
Richter, Davy, and my own, I conclude that 
fused nitre is constituted nearly of 47.5 pure 
acid, and 52.5 potash per cent. Having dis- 
solved 25 parts of this nitre in 100 water, I 
find the specific gravity, at 60% = 1.130, and 
consequently 110.6 measures of the solution. 
Any given nitric acid is saturated ivith pure 
carbonate of potash, and reduced to the spe- 
cific gravity of 1.130; the measure of the so- 
lution is then found, and hence we have data 

350 oxviJEN WITH Azorii;. 

to calculate the real acid in the said soliitian. 
Now, lOG grains of 1.51 nitric acid + 248 
grains of a solution of potash 1.482, with wa- 
ter, gave G65 grain measures of solution of 
nitre of 1.1 30 sp, gravity, indicating 150 of 
pure nitre. Hence 106 grains of the acid con- 
tained 71.2, or 67 per cent, which is 1^ per 
cent, less than Kirwan deduces it ; and this 
may partly arise from the escape of some acid 
by its mixture with water producing heat. 
Again, 133 grains of 1.42 acid were saturated 
with potash ; they gave 672 measures of 1.13 
solution, indicating 152 nitre; hence 133 acid 
contained 72 real, or 54 per cent, which nearly 
agrees with Kirwan's. Again, 205 grains of 
1.35 acid were saturated with 290 grains of 
1.48 carbonate of potash; this diluted gave 
850 measures of 1.13 solution, indicating 1S^2 
nitre ; that is, 205 grains acid contained 91 
Teal, 44.4 per cent, which also nearly agrees 
with Kirwan. Again, 224 grains of 1.315 
acid, took 300 grains of 1,458 carbonate of 
potash; thrs diluted gave 804 measures of 1.13 
solution, indicating 192 nitre; that is, 224 
grains of acid contained 86.5 real, = 38.6 per 
cent. ; this is extremely near Kirwan's es- 

Being thus satisfied with the near approxi- 
mation to truth of Kirwan's table of nitric acid 

yriTRIC ACID. 351 

I was notwithstanding desirous to discover, it 
possible, the sources of error which have in- 
fluenced the the conchjsions of Davy and Ber- 
thoilet on this subject, whose results are so 
different from each other and from those of 

That Mr. Davy has overrated the quantity 
of real acid in different solutions is manifest 
from this ; he finds the acid 1.504 to contain 
91.5 per cent. ; now, according to this, an 
acid of 1.55 would be nearly pure or free from 
water ; whereas nitric acid has been obtained 
of the specific gravity 1.62, without there be- 
ing any reason to suppose it was free from 
water. Mr. Davy's method of combining the 
elastic fluids nitrous gas and oxygen, in order 
to form nitric acid pure and free from v^ater in 
the first instance, and then combining the acid 
with a given portion of water, was certainly 
higlily ingenious, and it seems to have been 
executed with great care ; but that the results 
this way cannot be relied on, I am convinced 
from my own experience, some account of 
which will presently be given. But what ap- 
pears most surprising and unaccountable in his 
results, is, how the combination of 47.3 parts 
of his acid with 52.7 parts of potash should 
form nitre. He relates two experiments ; in 
one, 54 grains of 1.301 acid combined with 



potash, gave Q)(S grains of nitre, at 212% and 
this became 60 by fusion : in the other, 90 
grains of 1.504 acid, saturated with potash, 
gave 173 of dry nitre. — In all the similar ex- 
periments which I have made, I have uni- 
formly found only three quarters of the quan- 
tity of nitre said to have been obtained above, 
from given quantities of the acid. I conclude, 
therefore, that Mr. Davy must have committed 
some oversight in these two experiments, and 
that the direct formation of nitre from nitric 
acid and potash, accords only with Kirwan's 
estimate of the strength of nitric acid. 

Berthollet, in the Journal de Physique, 
March 1807, informs us, that he saturated 100 
parts of potash with nitric acid of 1.2978 
strength, and obtained 170 parts of nitre j he 
calculates the acid to contain 32.41 percent, 
real, by which we may infer that 216 grains 
of it were required. Nitre, according to this, 
would be 100 potash + 70 nitric acid, or 59 
potash + 41 acid per cent. This is much more 
potash than ever before was detected in nitre- 
How are we to be satisfied that the potash 
used contained no water ? If it contained any 
water, this would disappear in the process, 
and its weight be supplied by nitric acid, 
which would not be placed to the acid's ac- 
count. That this was the real fact I have no 


doubt ; 170 parts nitre are constituted of about 
89 potash, and 81 nitric acid ; the supposed 
100 parts of potash were, I conceive, 89 parts 
potash and 1 1 water, which of course caused the 
acid to be underrated by 1 1 parts.* To prove 
this, we have only to take a quantity of car- 
bonate of potash, such as is known to contain 
89 parts potash ; for instance, 170 parts of the 
dry neutralized carbonate, or 200 crystallized, 
which Berthollet rightly determines to contain 
89 parts of potash, and to this add 216 parts of 
the above nitric acid, and 170 nitre will be 
formed. This will also establish another fact 
worthy of notice ; namely, that the quantities 
of nitric and carbonic acid are the same to a 
given weight of potash. 

I shall now proceed to give the table of the 
strength of nitric acid. I have copied Kirwan 
for the strength due to each specific gravity, 

* Since writing the above, I have been faroured with 
the receipt of " Memoires de Physique et de Chimie de la 
Societe d'Arcueil. Tome 2." In this there is, amonsst 
other very important and valuable papers, one on the pro- 
portion of the elements of some combinations, by Ber- 
thollet. The author there determines, page 5i, that potasli 
kept for some time in fusion, still retains between 13 and 
14 per cent, of water. Hence, he admits the strength of 
nitric acid above given as his to be erroneous. In the 
sequel, he concludes that fused nitrate of potash contains 
51.4 potash and 48.6 nitric acid. 


except ihe first and second column, which hi« 
table has not, and the three last, where I think 
he has overrated the quantity of acid ; indeed, 
the lower part of his table is confessedly less 
correct. I have already given my reasons for 
considering his table as approximating nearest 
to the truth ; but have no doubt it might be 
made more correct ; I have, therefore, only 
extended the table to two places of decimals 
in the column of specific gravity. The column 
of acid per cent, by measure, will be found 
convenient for the practical chemist. The 
first column shews the number of atoms of 
acid and water in combination or collocation 
in each solution, agreeably to the preceding 
determinations j namely, an atom of acid is 
taken as 19.1 by weight, and an atom of wa- 
ter as 8. The last column exhibits the boiling 
points of the several solutions, as found by 
experiment. Those who wish to repeat these 
experiments, may be informed that a small 
globular glass receiver, of the capacity of 6 or 
7 cubic inches was used, 2 or 3 cubic inches 
of acid were put in, and then a loose stopper. 
It was then suspended over a charcoal fire. 
When signs of ebullition began to appear, the 
stopper was withdrawn, and a thermometer, 
previously adjusted at the boiling point of wa- 
ter, was inserted. It may be proper to oh- 



{;erve, that acids which have not previously 
been boiled, or which contain nitrous acid, 
usually begin to boil below 212° j but the va- 
pour soon escapes, and the temperature ad- 
vances to a stationary point. Nitric acid varies 
in specific gravity by temperature more than 
any other, as may be seen, page 44 ; there is, 
however, an error of the press in the table 
alluded to, for alcohol and nitric acid ; the 
numbers should be .11, and not .011. Every 
10" counts 6 upon the third place of decimals ; 
that is, if an acid be 1.516 at 50", it will be 
J. 51 at 60°. The expansion with me is uni^ 
iorm, and not variable as with Kirvvan. 

Table of the ijuantity of real acid in 100 parts of linui(J 
nitric acid^ at the temperature ct W 

AcM. \V.itcr 

Acid per cent. 
by weight. 

Acid per cent 
by measure. 

Specific gra- 

Soiling point 

J -f- 


175 ? 

1.75 } 


2+ 1 




100* > 

1-f. 1 













1+ 2 









1+ 3 





1+ + 





1+ 5 





1+ 6 










1+ 8 

23 • 


1 18 


1+ 9 





I +10 





1 + 11 





1 + 12 






Remarks on the above Table. 

1 . It seems not improbable, but that an acid 
free from water may be obtained, as repre- 
sented in the first line of the table. That such 
an acid would be in the liquid state, but with 
a strong elastic steam or vapour over it, at the 
common temperature, is most probable ; in 
this respect it would resemble ether, but per- 
haps be more volatile. Seventeen per cent, of 
water would bring it down to acid of the se- 
cond line, and such as has actually been ob- 
tained by Proust, This last would nearly 
agree with ether in volatility. With respect 
to the specific gravity of pure nitric acid, it 
must be less than 1.8 ; because a measure of 
that sp. gravity mixed with a measure of wa- 
ter, would make 2 measures of 1 .4, if there 
were no increase of density j and acid of this 
density is nearly half water.* I apprehend if 

* The theorem for specific gravities is -^ -j = j — ', 


where H represents the weight of the body ot greatest 
specific gravity, S its specific gravit)', L the body of least 
specific gravity, s its specific gravity, and / that of 
the mixture or pompound. Hence in the case above, 
1.8 1 _ 2.8 

1.8 ' 1 1.4. 


acid of the second line were distilled by a very 
gentle heat, when mixed with the strongest 
sulphuric acid, that probably an acid free from 
water would come over ; at least, a concen- 
tration is effected by such process in other 
cases of weaker acids. The receiver should 
be surrounded with a cold mixture. By dis- 
tilling an acid 1.31 off sulphuric acid, I got 
an acid 1.43 ^ and an acid of 1.427 treated in 
the same manner, gave an acid of 1.5. 

2. The acid in the second line, consisting 
of 2 atoms of acid and 1 of water, having only 
been obtained by one person, and not parti- 
cularly examined, we know of no peculiar 
properties it has, besides the specific gravity 
and boiling temperature ; but there can be 
little doubt that it possesses other properties 
which would distinguish it from all other 

3. The acid in the third line, consisting of 
1 atom of acid and 1 of water, has not often 
been obtained, and is therefore little known j 
it seems to be that acid which fused nitre, and 
the strongest possible sulphuric acid (such as 
it is to be had by that mode of concentration, 
which consists in boiling the common acid) 
would give by distillation. The water in this 
case, I suppose, is derived from the sulphuric 
acid, not from the nitre. It may, however. 


be oblained by repeated distillations of anjr 
acid above 1.42 ; provided there is a sufficient 
quantity of thar, and the first products always 
taken. What the di*itinguishing properties of 
this acid nay be» I have not had an oppoitunity 
of i^ivestigaling. 

4, The acid which consists of 1 atom of 
acid and 2 of water, is possessed of striking 
peculiarities. It is in fact that which consti- 
tutes a complete reciprocal saturation of the 
two elements. Evaporation produces no 
change in its constitution ; it distills as water, 
or any other simple liquid docs, without any 
alteration. It acquires the temperature 248° 
at boiling, which is greater than nny oiber 
compound of the two elements acquires. At 
any strength above this, the acid is most copi- 
ously elevated by heat ; at any stre-ngth below, 
the water is most easily raised. Pure water 
boils at 212° ; pnre acid perhaps at 30" ; the 
union of both produces a heavier atom than 
either, and requires a higher temperature for 
ebullition ; but in proportion as either prin- 
ciple prevails tnore than is necessary for satu- 
ration, then the temperature at ebullition is 
reduced towards that of the pure element it- 
self. Proust has observed that nitric acid of 
1 .48, produces no mo'-e effervescence with tin 
than with sand -, whereas the lower acids act 


most violently, as is well known. 'Hie fact I 
find as Proust states it. This would lead one 
to think that acid of 1.48 was of some peculiar 
constitution ; but I presume this characteristic 
of nitric acid belongs to that of 1.42, rather 
than 1.4 8 : not but that the former certainly 
acts on tin , but the explanation I conceive is 
this ; when the nitric acid in its action on me- 
tals is disposed to form ammonia, (an element 
constituted of one atom of azote and one of 
hydrogen united) 1 atom of nitric acid and \ 
of water are decomposed ; the 3 atoms of 
oxygen go to the metal, and the azote and 
hydrogen unite and form an atom of ammo- 
nia ; if, therefore, there were 1 atom of acid 
to 2 of water, there could be 1 atom of watev 
detached, which would of course join to the 
remaining acid, and dilute it the more ; but it 
there were 2 atoms of acid for 3 of water, 
then, detaching 3 atoms of oxygen, would 
leave an atom of nitrate of ammonia and 1 ot 
water, constituting the salt of that name, and 
one surplus atom of water. In this case, the 
remaining acid is not diluted with water by 
the process, lower than 1 to 2. Such acid, 
therefore, (which is about 1.47) is probably the 
lowest that can operate upon tin this way with- 
out any effervescence. 


5. The acid composed of 1 to 3 water, ha's 
not any peculiarity yet discovered. 

6. The acid of 1 to 4 water, is remarkable 
for being that which freezes the most easily of 
all, namely at — 2° of Fahrenheit, according 
to Cavendish. The strength of the acid is 
such, as that 1000 parts dissolve 418 of marble : 
Now, 418 of marble contain 228 of lime, and 
these require 370 or 380 of nitric acid, which 
therefore agrees with the acid of 1 to 4 water, 
and with that only. Above that strength, or 
below, the acid requires a greater cold to 
freeze it. — The inferior acids appear to have 
no remarkable differences, except such as the 
table shews ; but the temperature of freezing 
descends to some undetermined point, and then 
ascends again. 

7. The notion of those who consider the 
intensity of acid solutions to be proportionate 
to the quantity per cent, of the acid, or to their 
density, seems incorrect as far as nitric acid is 
to determine. It is true, the acidity or sour- 
ness of the solution, the power to produce ef- 
fervescence with carbonates, and perhaps 
other properties, increase nearly as the quan- 
tity or strength ; but the freezing and boiling 
temperatures, the action on metals, as tin, 
&c. have successive waves, and abrupt termi- 




nations, which indicate something very dif- 
ferent from that gradation in action which varies 
in the ratio of the quantity. 

I have frequently attempted to exhibit the 
nitric acid in a pure elastic form, and free 
from water, but have uniformly failed. Some 
account of the experiments may, notwith- 
standing, have its use. In order to form the 
nitric acid free from nitrous and oxynitric, I 
used large receivers and quantities of gas, 
amounting to some hundreds of cubic inches, 
and delivered the nitrous gas to the oxygen, 
and vice versa, in the centre of the receiver, 
and slowly : still the ratio of oxygen to nitrous 
gas was variable. The experiments were 
made over water. Wishing to exclude water 
as much as possible, I procured some globular 
receivers, containing from 15 to 60 cubic 
inches ; to these stopcocks were adapted, so 
as to connect them with the air-pump or with 
other receivers. These were first filled with 
oxygen gas or common air, and then partially 
exhausted ; afterwards they were connected 
with receivers over water, containing known 
quantities of nitrous gas, and a communication 
opened j the moment after the nitrous gas had 
entered the globe, the cock was turned ; great 
eare was taken to dry the globe previously to 
the experiment, and to prevent any water en- 


tering with the air, (except the steam which 
gases commonly have, the quantity of which is 
easily ascertained for any temperature). The 
instant the two f^ascs were mixed, the globe 
was filled with dense orange coloured gas, 
which continued without any change ; a dewy 
appearance on the inside of the glass was al- 
ways perceived, consisting, no doubt, of con- 
densed acid and water. 

The results of the experiments are below : 

oxygen. nitrous gas. percent. 

measure look 1.8, residuary 13.6 oxyg. 
■ " 2.11 6. nitrous 






1 44- 27. oxyg. 

1.83 4. 

2.29 2.5 nitrous 

1.61 7.6 oxyg. 

1.65 9.3 nitrous 

1.8 2.5 oxyg. 

The residuary gas was examined after letting 
in water, and washing away the acid. From 
these results, it is evident the quantity of ni- 
trous gas combining with a given volume of 
oxygen in such circumstances, is extremely 
variable, and much like what takes place in 
small quantities in tubes. The coloured gas 


is always, I apprehend, either nitrous or oxy- 
nitric acid ; the nitric acid vapour is without 
colour, and condenses along with the steam 
on the sides of the vessel ; but the o;her acids 
instantly colour the liquid. By inclosing a 
manometer, I endeavoured to find the elastic 
force, and the specific gravity of the aerial 
acids ; but from the liquid condensation of a 
part, I found the specific gravity variable, and 
always too much. It was commonly about 
three times that of atmospheric air. Mr. Davy 
combined 1 measure of oxygen with 2.32 of 
nitroiis gas, leaving an excess of oxygen, and 
calculated the specific gravity of the aerial 
product at 2.1-4 ; but it is more than probable 
that this is overrated for the reasons just men- 
tioned. Reasoning by analogy, nitric acid 
gas should be of the same weight as carbonic 
acid gas, as its atom is of the same weight; or 
about the same as nitrous oxide and muriatic 
aci'.l ; hence we may infer, till it can be ascer- 
tained experimentally, that the specific gravity 
of pure nitric acid, in the clastic state, is be- 
tween 1.5 and 2. Nitrous acid is probably 
about 2.5, and oxynitric about 2 or 2.25. 

I was in hopes to ascertain the constitution 
of nitric ticid, by decompobing nitre by heat, 
and finding the ratio of azote to oxygen ; but, 
as has been observed by others, the air is of 


different qualities at different periods of the de- 
composition. By one experiment, I obtained 
about 30 grains of air from 100 of nitre in an 
iron retort ; it was received in 5 portions: the 
first contained 70 per cent, of oxygen, agree- 
ing with the constitution of nitrrc acid exhi- 
bited in the table, page 331 ; but the suc- 
ceeding portions gradually fell off, and the last 
contained only 50 per cent, oxygen. 

It may be proper to remark, that the nitric 
acid of commerce is sold under the names of 
double and single aqua fortis ; the former is 
intended to be twice the strength of the latter; 
the absolute strength of double aqua fortis is 
not, I believe, uniform. It commonly runs 
between the specific gravities k^^ 1,3 and 1.4. 

4. Oxijnitric Acid. 

The existence of oxynitric acid is inferred 
from the combination of oxygen and nitrous 
gas, in the second experiment, page 328 ; at 
least an acid product is obtained, containing 
more oxygen than is found in nitric acid. As 
yet I have not been able to obtain this acid 
any other way, and therefore have not had an 


opportunity of examining its properties, ex- 
cept upon a very small scale. I thought that 
distilling the common nitric acid from the 
oxide of manganese might afford an acid more 
liighly oxydized ; but I obtained a product 
yielding the fumes of oxymuriatic acid, owing 
no doubt to the muriatic acid previously in the 
nitric ; for, by boiling, these fumes vanished, 
and left nothing but nitric acid, as far as ap- 
peared. The acid obtained from the gases 
abovementioned, is only at best one half oxy- 
nitric, and the other half nitric, so that it is 
still but a mixture. 

A dilute solution of the acid obtamed by 
mixing nitrous and oxygen gas as above, 
seems to possess similar properties to nitric 
acid solutions. It is acid to the taste, changes 
vegetable blue to red, and neutralizes the al- 
kalies ; whether in this last case it parts with 
its excess of oxygen, I have not determined. 
The atom of oxvnitric acid must, it is pre- 
sumed, weigh 26.1 ; it consists of 1 atom of 
azote and 3 of oxygen. The specific gravity 
of the acid in an elastic state is probably 
about 2 or 2i. 


5. Citrous Acid. 

The compound denominated nitrous acid, 
is obtained by impregnating liquid nitric acid 
with nitrous gas. This acid, however, is 
never pure nitrous acid, but a mixture of 
nitric and nitrous ; as is evident by boiling it, 
when the nitrous is driven off, and the nitric 
remains behind. Pure nitrous acid seems to 
be obtained by impregnating water with oxy- 
genous gas, and then with nitrous gas ; in this 
way 1 measure of oxygen takes about [^^ of 
nitrous ; that is, 1 atom of oxygen takes 2 
atoms of nitrous gas to form 1 of nitrous 
acid. The weight of the atom therefore 
is 31.2. 

By repeated trials I find that 100 measures 
of nitric acid of 1.30 specific gravity, agitated 
with nitrous gas, takes up about 20 limes its 
bulk of the gas. If the acid be of twice the 
strength, or of half the strength, it makes little 
difference j the quantity of gas is nearly as the 
real acid, within certain limits of specific gra- 
vity. Very dilute acid (as 1 to 300 water) 
seems to have scarcely any power of absorbing 
nitrous gas, besides what the water itself has. 
Hence, it seems that what we call nitrous acid. 


IS only about ^ih of it real acid ; the rest is 
nitric acid. 

Mr. Davy concludes, that the bright yellow 
acid of 1.50 specific gravity, contains nearly 3 
per cent, of nitrous gas ; the dark orange 5|, 
and the blue green 8 ; the two last being of 
the strength 1.48 or 1.47. 

From the experiments of Priestley, it is evi- 
dent that the nitrous acid, or as he called it, 
the phlogistic at ed nitrxnis vapour, is much more 
volatile than nitric acid ; or, to speak more 
properly, has less affinity for v\rat-er. Hence the 
fuming of the nitrous acids in great part arises. 
This is further corroborated by the ready ebul- 
lition of those acids. The acid which I ob- 
tained above by saturating nitric acid of 1.30 
with nitrous gas, was dark orange, and strongly 
fuming : it boiled at IGO''; whereas the nitric 
acid of the same strength boils at 236°. It is 
owing to the same cause that very dilute ni- 
trous acid exhibits the characteristic smell of 
the acid ; but equally dilute nitric acid has no 
smell. When nitrous acid is diluted so far as 
to contain just its owr. bulk of nitrous gas, it 
then attracts oxygen, but very slowly ; it re- 
quires as much agitation as sulphuret of lime to 
saturate it. 

It does not appear that pure nitrous acid 


combines with the alkalies so as to form dry 
salts or nitrites s the concentrated solutions 
seem to lose the nitrous gas, and then the ni- 
traies are obtained. 



There are two compounds of oxygen and 
carbone, both elastic fluids j ttie one goes by 
the name of carbonic acid, the other carbonic 
oxide ; and it appears by the most accurate 
analyses, that the oxygen in the former is just 
double what it is in the latter for a given 
weight of carbone. Hence, we infer that one 
is a binary, and the other a ternary compound ; 
but it must be enquired which of the two is 
the binary, before we can proceed according 
to system. The weight of an atom of carbone 
or charcoal, has not yet been investigated. 
Ot the two compounds, carbonic acid is that 
which has been longest known, and the pro- 
portion of its elements more generally investi- 
gated. It consists of nearly 28 parts of char- 
coal by weight, united to 72 of oxygen. Now 



as the weight of an atom of oxygen has been 
determined already to be 7 ; we shall have the 
weight of an atom of carbone = 2.7, supposing 
carbonic acid a binary compound ; but 5.4, if 
we suppose it a ternary compound. 

Carbonic acid is of greater specific gravity 
than carbonic oxide ; and on that account, it 
may be presumed to be the ternary or more 
complex element. It must, however, be al- 
lowed, that this circumstance is rather an in- 
dication than a proof of the fact. The ele- 
ment of charcoal may be so light, that two 
atoms of it with one of oxygen, may be speci- 
fically lighter than one with one. But there 
are certain considerations which incline us to 
believe, that the element of charcoal is not 
much inferior to oxygen in weight. Oils, al- 
cohol, ether, wood, &c. are compounds into 
which hydrogen and charcoal principally enter; 
these are a little lighter than water, a com- 
pound of hydrogen and oxygen. Though 
charcoal in a state of extreme division is rea- 
dily sublimed by heat, it does not assume the 
form of a permanently elastic fluid, which one 
would expect of a very light element. Besides, 
carbonic acid is the highest degree of oxidation 
of which charcoal is susceptible, as far as we 
know ; this rarely happens under two atoms of 
oxygen. Carbonic acid is easily resolved by 


electric shocks Into oxygen and carbonic 
oxide ; but carbonic oxide does not appear to 
be resolved in the same mode into charcoal 
and carbonic acid, which one might expect 
from a triple compound. Or^e ot the most 
common ways of obtaining carbonic oxide, is 
to decompose carbonic acid by some substance 
possessing affinity for oxygen ; now, oxygen 
may be abstracted from a body possessing two 
atoms of it more easily than from one posses- 
sing only one. On all these accounts, there 
can scarcely be a doubt that carbonic oxide is 
a binary, and carbonic acid a ternary cora^ 

1. Carbonic Oxide. 

This gas was discovered by Dr. Priestley ; 
but its distinguishing features were more fully 
pointed out by Mr. Cruickshanks, in an essay 
in Nicholson's Journal, 1801. Aibout the 
same time, another essay ot Desormes and 
Clement was published in the Annales de 
Chemie, on the same subject. These essays 
are both of great merit, and highly creditable 
to their authors. Before that time, carbonic 
oxide had been confounded with the combus- 
tible gases composed of carbone and hydrogen j 


but Cruickshanks and Desormes distinctly de- 
monstrated, that in the combustion of this gas 
nothing but carbonic acid was produced ; and 
that the quantity of oxygen requisite for its 
combustion, was not more than half of that 
afterwards contained in the carbonic acid j 
they, therefore, rightly concluded that the gas 
was a compwDund of carbone and oxygen, since 
which it has been known by the name of car- 
bonic oxide. 

Carbonic oxide may be procured by various 
processes j but it is mostly acconipanied with 
one or more foreign gases, from some of which 
it is difficult to separate it ; for this reason, 
when it is wanted pure, such methods must 
be used as give it mixed with gas that can be 
extracted. The following process answers 
well : Let equal weights of clean, dry iron 
filings and pulverized dry chalk, be mixed 
together, and put into an iron retort j let the 
retort be heated red, and the heat gradually 
increased ; gas will come over copiously, 
which may be received over water ; this gas 
will be found a mixture of perhaps equal parts 
of carbonic oxide and carbonic acid j the last 
.nay be extracted by due agitation in a mix- 
ture of lime and water; \yhat remains is pure 
carbonic oxide, except 2 or 3 per cent, of 
common air, from the lime water. The theory 


of this process is manifest ; chalk consists of 
carbonic acid and lime ; the carbonic acid is 
disengaged by heat, and is immediately ex- 
posed to the red hot iron, which in that state 
has a strong affinity for oxygen ; the carbonic 
acid parts with one half of its oxygen to the 
iron, and the residue is carbonic oxide ; but 
part of the acid escapes along with it unde- 
compounded. With a proper apparatus, the 
gas may be procured by transmitting carbonic 
acid repeatedly over red hot charcoal in an iron 
or porcelain tube. 

This gas may be obtained, by exposing to a 
red heat, a mixture of charcoal with the oxides 
of several metals, or with carbonate of lime, 
barytes, &c. Bat there is great danger in this 
way of procuring some hydrogen, and carbu- 
retted hydrogen, along with carbonic oxide 
and acid. Indeed, all gas procured from 
wood and from moist charcoal, is a mixture of 
these four, varying in proportion according to 
the heat and the continuance of the process. 

According to Cruickshanks, the specific 
gravity of carbonic oxide is .956 ; according 
to Desormes and Clement, .924. Appre- 
hending that they had both rated it too low, 
I carefully found the specific gravity of a mix- 
ture of 6 parts carbonic oxide and 1 common 
air, at two trials j in one it came out .945, 


and in the other .94 ; I conceive, then, that 
.94 may be taken as a near approximation to 
the truth ; it is just the mean of the two au- 
thors above. Carbonic oxide is fatal to ani- 
mals that breathe it ; it is combustible, and 
burns with a fine, clear, blue flame, without 
any smoke or the least appearance of dew, if 
a bell glass is held over the flame. This cir- 
cumstance, amongst others, distinguishes it 
clearly from all gases containing hydrogen, 
either mixed or combined. When mixed with 
oxygenous gas, or common air, in Volta's eu- 
diometer, it explodes with an electric spark, 
and is converted into carbonic acid. Ihe cir- 
cumstances attending the explosion are some- 
what remarkable j unless the carbonic oxide 
amount to at least jth of the mixture, it will 
not explode ; and the oxygen must be at 
least -T-V^h of the mixture. Besides, it fre- 
quently happens, when common air is used 
for oxygen, that a smart explosion takes place, 
and yet both carbonic oxide and oxygen shall 
be found in the residuum. This circumstance 
disappears if the oxygen be above 30 per cent 
pure. It should be observed, that whenever 
proportions near the extremes above noted, are 
used, the results become ambiguous ; as a par- 
tial combustion sometimes happens. When 


100 measures of carbonic oxide are mixed 
vvitli 250 of common air, (in which case the 
whole of the combustible gas should combine 
with the whole of the oxygen) a smart explo- 
sion ensues by the .first spark ; but only -^ds of 
the gas is burnt ; the rest, and a corresponding 
proportion of oxygen, remain in the residuum. 
AVhen plenty of combustible gas and a mini- 
mum of oxygen are exploded, the whole of 
the oxygen usually disappears. 

Carbonic oxide does not explode by elec- 
tricity when mixed with oxymuriatic acid, at 
least in any instance I have had, unless a small 
portion of common air be present ; but the 
mixture being exposed to the sun, a diminution 
soon takes phce ; if the light be pov/erful, 5 
or 10 minutes are sufficient to convert 100 
grain measures of the gas along with iOO of 
the acid, into carbonic and muriatic acids. I 
have n' t been able to determine, from the 
lateness of the season (October), whether the 
mixture Would explode by the solar light. 

Pure carbonic oxide is not at all affected by 
electricity. 1 was present when Dr. Henry 
conducted an experiment, in which 35 mea- 
sures of carbonic oxide received 1 100 small 
shocks ;- no change of dimensions took place ; 
there was no carbonic acid formed, nor oxy- 


gen liberated ; but the residuary gas being 
fired with oxvgen appeared to be pure car- 
bonic oxide. 

Water absorbs ^Vth of its bulk of carbonic 
oxide. It will be seen by reference to page 
201, also to the Manchester Memoirs, vol. 1.- 
nnc Series, pages 272 and 436, that this gas 
has perplexed me more than any other, at dif- 
ferent periods, as to what class to refer it, in 
regard to absorption. One reason was-, that 
in mv more early experiments I used sometimes 
to obtain carbonic oxide by means of charcoal ; 
in which case it was doubtless mixed with 
more or less of hydrogen ; another reason was, 
that I did not agitate the water long enough ; 
this gas requires longer agitation than any 
other I have met with. 1 can now make 
water take up full .V^h of its bulk, or at 
least in that proportion, according to the [)urity 
of the incumbent gas. 

The proportion of carbone and oxygen foimd 
in carbonic oxide, has been found by experi- 
ment as under : 

measures. measures. measuies. 

Cruickshanks — iGOcarb.ox. — take40oxy. 
Dcsormes&Cltm.lOO — 79 — '-'>(> — 

_ _ _ 83 — 34 — 

My own exp. - 100 — 91- — 47 — 


Cruickshanks certainly underrates the oxy- 
gen ; I always find the oxygen fully equal to 
half the carbonic acid, whether fired over mer- 
cury or water. Desofmes' experiments were 
made over water, and are therefore rather un- 
certain as to the quantity of acid ; they have 
evidently used impure gas. Their first result 
given above is the mean of nine experiments ; 
the other two are extremes in regard to acid 
and oxygen (Annales de Chimic 39 — page 38). 
It is remarkable, that in one of their deduc- 
tions (page 44), on which they seem to rely 
most, they find the carbone 44, and the oxy- 
gen 56 parts : by a previous experiment, they 
had found carbonic acid to- consist of 28.1 car- 
bone, and 71.9 oxygen (page 4l); that is, of 
41- carbone, and 112 oxygen : where the oxy- 
gen is just double of that in the carbonic oxide 
to a given quantity of carbone. This most 
striking circumstance seems to have wholly 
escaped their notice. 

The exact composition of this gas is easily 
ascertained by exploding it with common air 
over water. Let 2 parts of the gas be mixed 
with 5 of air, and fired ; the residuum must 
be washed in lime water, and the quantity left 
accurately noted ; then apply a small portion 
of nitrous gas to the residuum, sufficient to take 
out the oxygen ; hence we have data to find 


the quantity of the two gases which have com- 
bined to form carbonic acid. In this way, 10 
measures cf oxide will be found to take from 
4.5 to 5 measures of oxygen. 

The conclusion then is, that carbonic oxide 
in its combustion, requires just as much oxy- 
gen as it previously has in its constitution, in 
order to be converted into carbonic acid. This 
agrees too with the results derived from the 
specific gravity of the gas. The gas may be 
considered as lid!/ burned charcoal ; it bears 
the same relation to carbonic acid as nitrous 
gas does to nitric acid. An atom of carbonic 
oxide consists then of one of carbone or char- 
coal, weighing 5.4, and one of oxygen, weigh- 
ing 7, together making 12.4. The diameter 
of the atom, in an elastic state, is 1 .02, that 
of hydrogen being unity. Or, 106 measures 
of the gas contain as many atoms as 100 mea- 
sures of hydrogen.* 

* It will, perhaps, be expected that some notice should 
be takefi here of the opinion of Beilhollet, that carbonic 
oxide is a compound of carbone, oxygen, and hydrogen, 
and therefore, may be denominated oxy carburet ted hydrogen. 
It was formerly his opinion that certain gases consist of 
carbone and hydrogen, and hence are called carburettcd 
hydrogen ; others consist of carbone, oxygen, and hydrogen, 
and are denominated as above. But in the 2d volume of 
the Memoirs d'Arcueil, he contends that all the combustible 


2. Carbonic Acid. 

The gas now denominated carbonic acid, 
has been recognised as an elastic fluid distinct 
from atmospherical air, for a longer time per- 
haps than any other. It may be said to have 

gases thai have been considered as belonging to these two 
species, are in fact oxycarbmctted hydrogen ; and that 
these elements are combined in an indefinite variety of pro- 
portions. That the combustible gases produced from moist 
charcoal and other bodies, contain oxygen, carbone, and 
hydrogen in various proportions, is a fact of which no ex- 
perienced person can doubt ; but it has not yet been 
shewn satisfactorily by any one, that they cannot be made 
by mixing certain proportions of two or more of the fol- 
lowing distinct species, namely, cnrburelted hydrogen (of 
stagnant water), carbonic oxide, olcfiant gas, and hydrogen. 
— As for carbonic oxide, whilst it remains an indisputed 
fact, that in the combustion of it nothing hut carbonic acid is 
produced, and that equal in lueight to the carbonic oxide 
and the oxygen, it will require very specious reasoning to 
convince any one that it contains either hydrogen, sulphur, 
or phosphorus ; unless it be first proved that carbonic acid 
contains the same. One argument of Berthollet is, how- 
ever, more ingenious than any reply to it which has ap- 
peared : it is this, a compound elastic Jluid ought lobe found 
specifically heavier than the lighter of the two elementary 
fiuidi conelitutin^: it. This is, as far as I know, universally 
true ; but it does not follow th^t carbonic oxide should be 
specifically heavier than oxygenous gas. An atom of char- 


been known, though very imperfectly, to the 
ancients. Towards the close of the last cen- 
tury, almost all the distinguished chemists had 
occasionally turned their attention to this ar- 
ticle, and its properties became gradually de- 
veloped. It has received at times dilTerent 
names ; namely, cJioak damp, ^fijced a/?', aerial 
acid, mephitic, and calcareous acid. 

coal, it appears, is lighter than an atom of oxygen ; it is 
probable, then, it would make a lighter elastic fluid., could 
we convert it into one by a due degree, ol heat. We cannot 
judge of the specific gravity of an elastic fluid either from 
the weight of the article in a solid or liquid form ; or from 
the degree of heat re(|uisite to produce the elastic state. 
Water is certainly heavier than charcoal ; yet it produces 
a light elastic fluid. Ether is lighter than water ; but it 
produces a heavier elastic fluid, and at a lower temperature. 
Carbonic oxide may be lighter than oxygen, for the same 
reason that nitrous gas. is lighter than oxvge n ; nameiy, be- 
cause oxygen is the heavier of the two elemenls that enter 
into its composition. The answers above alluded to deny the 
generality of the argument ; they produce what ihey con- 
ceive a parallel case in nitrous oxide, and nitrons gas ; and 
allege that oxygen, the heavier of tlfe two component ele- 
ments, being abstracted from nitrous gas, leaves nitrous 
oxide, which is specifically heavier than nitrous gas. But 
if the doctrine we have advanced on this head be true, they 
liave mistaken /w// of the operation for the whole; in the 
conversion alluded to, not only the oxygen is taken from 
an atom of the nitrous gas, but at the same moment, the 
azote is joined to another atom of the nitrous gas to form one 
of nitrons oxide. 


Carbonic acid gas is formed by burning char- 
coal ; but it is most easily obtained in a pure 
state from chalk, or some of the carbonates, 
by means of dilute sulphuric or other acid ; it 
may be received in bottles over mercury or 
water, but the latter absorbs a portion. — This 
gas extinguishes flame, and is unfit for respira- 
tion J its specific gravity is nearly 1.57, as ap- 
pears from the experience of all who have 
tried : 100 cubic inches, at the pressure of 30 
inches of mercury, and temperature of 60% 
weigh from 47 to 48 grains. Carbonic acid is 
frequently produced in mines, and in deep 
wells : it is known to workmen by the name 
of dioak damp, and proves fatal to many of 
them ; it is also constantly found in the atmo- 
sphere, constiiuting about -r^j^tb part of the 
whole ; its presence is easily detected by lime 
water, over which it forms a film iilmost in- 
stantly. iv\ the breathing of animals this gas 
is constantly produced ; about 4 per cent, of 
the air expired by man, is usually carbonic 
acid, and the atmospbcric air inspired loses the 
same quantity of oxygen. 

Water absorbs just its own bulk of carbonic 
acid gas ; that is, the density of the gas in the 
water after agitation, is the same as the density 
of the incumbent gas above, and the elasticity 
of the gas in the water is unimpaired. The 

CARftONiC ACID. 581 

water so impregnated has the taste and other 
properties of an acid. This gas is the product 
of fermentation, and gives to fermented liquors 
their brisk and sparkling appearance ; but it 
soon escapes from liquids, if they are exposed 
to the air. 

Carbonic acid combines with alkalies, earths 
and metallic oxides, and forms with them salts 
called carbonates. Lime water, by agitation 
with any gas containing carbonic acid, be- 
comes milky, owing to the generation of chalk 
or carbonate of lime, which is insoluble in 
water. Hence this water is an elegant test of 
the presence of carbonic acid. 

The constitution of this gas can be shewn 
both by synthesis and analysis : but more con- 
veniently by the former. The experiments of 
Lavoisier, Crawford, Desormes and Clement, 
and more recently those of Allen and Pepys, 
on the combustion of charcoal in oxygen gas, 
have left no doubt as to the quantity of the 
elements in carbonic acid ; 28 parts of char- 
coal by weight unite to 72 of oxygen, to form 
lOO of carbonic acid, very nearly. In this 
case too, it is remarkable that the volume of 
carbonic acid is the same as that of the oxygen 
entering into its constitution. Tennant has 
shewn that carbonic acid may be decomposed ; 
by heating phosphorus with carbonate of Wmt, 


phosphate of lime and charcoal were ob- 

Carbonic acid is decomposed by electricity 
into carbonic oxide and oxygen. I assisted 
Dr. Henry in an experiment by which 52 
measures of carbonic acid were made 59 mea* 
sures by 750 shocks j the gas after being 
washed became 25 measures ; whence these 
had arisen from the decomposition of 18 mea- 
sures of acid ; these 25 measures consisted of 
16 carbonic oxide and 9 oxygen ; for, a por- 
tion being subjected to nitrous gas, manifested 
4d of its bulk to be oxygen ; and the rest was 
fired by an electric spark, and appeared to be 
almost wholly converted into carbonic acid. 

Carbonic acid then appears to be a ternary 
compound, consisting of one atom of charcoal 
and two of oxygen j and as their relative 
weights in the compound are as 28 : 72, we 
have 36 : 28 : : 7 : 5.4 = the weight of an 
atom of charcoal ; and the weight of an atom 
of carbonic acid is 19.4 times that of hydrogen. 
The diameter of an atom of the acid in an 
elastic state is almost exactly the same as that 
of hydrogen, and is therefore represented by 
1 ; consequently a given volume of this gas 
contains the same number of atoms as the same 
volume of hydrogen. 




Two distinct compounds of oxygen and sul- 
phur have been for some time universally re- 
cognized ; but there exists a third, the nature 
and properties of which are yet in a great mea- 
sure unknown. According to the received 
principles of nomenclature, the first, denoting 
the lowest degree of oxidizement of sulphur, 
may be called sulphurous oxide, or the oxide 
of sulphur ; the second, denoting a higher 
degree, sulphurous acid ; and the third or 
highest degree known, sulphuric acid. 

1. Sulphurous Oxide. 

The existence of oxide of sulphur in a com- 
bined state was first observed by Dr. Thomson. 
By sending oxymuriatic acid in the gaseous 
state, through a vessel containing flowers of 
sulphur, he obtained a red liquid, which he 
denominated sulpliuretted muriatic acid j but 
it would have been more properly called 7nu- 


riate of sulphur } as its formation is similar to 
that of muriate of iron, &c. in like circum' 
stances. Now, it has been shewn ihat oxy- 
muriatic acid is muriatic acid united to oxygen, 
one atom to one; hence the atom of oxygen 
oxidizes an atom of sulphur, and the muriatic 
acid unites to the oxide, forming muriate of 
sulpliur, or more strictly muriate of oxide of 
sulphur. This oxide of sulphur. Dr. Thomson 
finds, is not easily obtained separate ; for when 
the red liquid is poured into water, the oxide 
resolves itself into sulphur and sulphuric acid. 
(Xicholson's Journal, vol. G — 101-.) 

When sulphuretted hydrogen gas and sul- 
phurous acid gas are mixed over mercury, in 
the proportion of 6 measures of the former to 5 
of the latter, both gases lose their elasticity, 
and a solid deposit is made on the sides of the 
tube. The common explanation given of this 
fact is, that the hydrogen of the one gas unites 
to the oxygen of the other to form water, and 
the sulphur of both gases is precipitated. This 
explanation is not correct ; water is indeed 
formed, as is stated ; but the deposition con- 
sists of a mixture of two solid bodies, the one 
sulphur, the other sulphurous oxide : they may 
be distinguished by their colour 3 the former is 
yellow, the latter bluish white ; and when 
th^y are both thrown into water, the former 


soon falls down, but the latter remains for a 
long time suspended in the water, and gives 
it a milky appearance, which it retains after 
filtration. It will appear in the sequel, that 5 
measures of sulphurous acid contain twice as 
much oxygen as the hydrogen in 6 measures 
of sulphuretted hydrogen require j it follows, 
therefore, that one half of the oxygen ought 
still to be found in the precipitate, which 
accords with the above observation. Again, 
if water, impregnated with each of the gases, 
be mixed together till a mutual saturation takes 
place, or till the smell of neither gas is ob- 
served after agitation, a milky liquid is ob- 
tained, which may be kept for some weeks 
without any sensible change or tendence to 
precipitation. Its taste is bitter and somewhat 
acid, very different from a mere mixture of 
sulphur and water. When boiled, sulphur is 
precipitated, and sulphuric acid is found in 
the clear liquid. The milkiness of this li- 
quid seems therefore owing to the oxide of 

It may be proper to remark that the white 
flowers of sulphur, commonly sold by the 
druggists, are not the oxide of sulphur. They 
are obtained by precipitating a solution of sul- 
phuret of lime by sulphuric acid. They consist 
of 50 per cent, sulphate of lime and 50 of sul- 


phur, in some state of combination with the 
sulphate ^ for, the two bodies are not separable 
by lixiviation. 

When sulphur in a watch glass is ignited, 
then suddenly extinguished, and placed on a 
stand over water, and covered with a receiver, 
the sulphur sublime? and fills the receiver with 
white fumes. On standing for some minutes 
or an hour, the sulphur gradually subsides, 
and forms a fine yellow film over the surface of 
the water. The air in the receiver loses no 
oxygen by this process. But when sulphur 
ignited, is placed in the circumstances above- 
mentioned, it burns with a fine blue flame, 
emitting some bluish white fumes, scarcely 
perceptible at first ; as the combustion con- 
tinues these fumes increase, and towards the 
conclusion, when the oxygen begins to be de- 
ficient, they rise up in a copious stream, and 
fill the receiver so that the stand is scarcely 
visible. It a portion of the air is passed 
through water, it still continues white. In 
the space of an hour the air in the receiver be- 
comes clear ; but no traces of sulphur are seen 
on the surface of the water. The whiteness in 
this last case does not, therefore, seem to arise 
iro.m sublimed sulphur, but from the oxide of 
sulphur, which is formed when there is not 
oxygen sufficient to form sulphurous acid ; ths 


last is known to be a perfectly transparent elastic 
fluid. Whether the sulphurous oxide in this case 
is absorbed by the water in that state, or is gra- 
dually converted into sulphurous or sulphuric 
acid, I have not been able yet to determine. 

When a solution of sulphuret of lime has 
been exposed to the air for a few weeks, till it 
becomes colourless, and sulphur is no longer 
precipitated, if a little muriatic acid be added 
to it, the whole becomes milky, and exhales 
sulphurous acid ; after some time sulphur is 
deposited, and the sulphurous acid vanishes, 
leaving muriate of lime in solution. This 
milkiness must be occasioned by sulphurous 
oxide ; for, sulphite of lime, treated in like 
manner, exhibits no such appearance. 

As far, then, as appears, sulphurous oxide 
is a compound of one atom of sulphur and one 
of oxygen; it is capable of combining with 
muriatic, and perhaps other acids ; when sus- 
pended in water, it gives it a miiky appear- 
ance and a bitter taste, and the mixture being 
heated, the oxide is changed into sulphur and 
sulphuric acid. An atom of sulphur being 
estimated, from other considerations hereafter 
to be mentioned, to weigh 13, and one of oxy- 
gen weighing 7, it will follow that oxide of 
sulphur is constituted of 65 sulphur and 35 
oxygen per cent. 


2. Sulphurous Acid. 

When sulphur is heated to a certain degree 
in the ooen air, it takes fire and burns with a 
blue flame, producing by its combination with 
oxygen an elastic fluid of a well known and 
highly suffocating odour ; the fluid is called 
sulphurous acid. Large quantities of this acid 
are produced by the combustion of sulphur in 
close chambers, for the purpose of bleaching 
or whitening flannels and other woollen goods. 
In this way, however, the acid never consti- 
tutes more than 4 or 5 per cent, of the volume 
of air, and is therefore much too dilute for 
chemical investigations. It may be obtained 
nearly pure by the following process : To two 
parts of mercury by weight put one part of 
concentrated sulphuric acid in a retort; apply 
the heat of a lamp, and sulphurous acid gas 
will be produced, which may be received 
over mercury. The reason of this is, each 
atom of mercury receives an atom of oxygen 
from one of sulphuric acid, and the remainder 
of the sulphuric atom constitutes one of sul- 
phurous acid, as will be evident from what 


Sulphurous acid is unfit for respiration and 

for combustion : its specific gravity, according 


to Bergman and Lavoisier, is 2.05 ; according 
to Kirwan, 2.24 ; by my own trials, it is 2.3. 
I sent a stream of the gas, after it had passed 
through a cold vessel connected with the re- 
tort, into a flask of common air ; this was after- 
wards weighed, and the quantity of acid gas 
then ascertained by water ; it appeared by two 
trials, agreeing with each other, that 12 ounce 
measures of the gas weighed 9 grains more 
than the same quantity of common air, and 
this last weighed 7 grains nearly. — Water ab- 
sorbs about 20 times its bulk of this gas at a 
mean temperature, according to my expe- 
rience ; but some say more, others less. The 
quantity absorbed, no doubt, will be greater 
as the temperature is less. Hence, it seems 
that water has a chemical affinity for the gas ; 
but the whole of it escapes if long exposed to 
the air, except a small portion which is con- 
verted into sulphuric acid. 

When water, impregnated with sulphurous 
acid, is exposed to oxygen in a tube, the oxy- 
gen is slowly imbibed, and sulphuric acid 
formed. In twelve days, 150 measures of the 
acid, absorbed by water, took 35. of oxygen, 
leaving a residuum of oxygen and sulphurous 
acid. When sulphurous acid gas and oxygen 
gas are mixed and electrified for an hour over 
mercury, sulphuric acid is formed; but 1 do 


not find that the proportion oF the elements of 
the acids can in this way be ascertained ; for, 
the mercury becomes -oxidized, and conse- 
({uently liable to form an union with either of 
the acids. — The two gases also combine, when 
made to pass through a red hot porcelain tube. 
Sulphurous acid is said to be decomposed by 
hydrogen and charcoal at a red heat ; sulphur is 
deposited, and water or carbonic acid formed, 
according as the case requires. When a mea- 
sure of oxymuriatic acid gas is put to a measure 
of sulphurous acid gas, over mercury, the sul- 
phurous acid is converted into sulphuric ; but 
no exact result can be obtained, from the rapid 
action of the former gas on mercury. 

Sulphurous acid oxidizes few of the metals ; 
but it possesses the common properties of acids, 
and unites with the alkalies, earths, and me- 
tallic oxides, forming with them salts deno- 
minated sulphites. 

It remains now to investigate the number 
and weight of the elements in sulphurous acid. 
I have made a great number of experiments 
on the combustion of sulphur in atmospheric 
air, in various circumstances ; but those I 
more particularly rely upon, were made in a 
receiver containing 400 cubic inches : it was 
open at top, and had a brass cap, by means of 
whicl) an empty bladder could be attached to 


the receiver, in order to receive the expanding 
air ; a small stand was provided, and a watch 
glass was placed on it, filled with a known 
weight of the flowers of sulphur ; the whole 
was placed on the shelfof a pneumatic trough, 
and as soon as the sulphur was lighted by on 
ignited body, the receiver was placed over it, 
with its margin in the water ; the combustion 
was then continued till the blue 6ame expired ; 
near the conclusion, white fumes arise copi- 
ously, and fill the receiver. A small phial 
was then filled with water, inverted, and care- 
fully pushed up into the receiver to withdraw 
a portion of air for examination ; the receiver 
was then removed, and the loss of sulphur 
ascertained. The residuary gas in the phial 
was fired with hydrogen in Volta's eudiometer. 
The loss of sulphur at a medium was 7 grain?, 
and the oxygen in the residuary gas was at a 
medium 16 per cent, or rather more ^ the 
weight of oxygen, therefore, which had dis- 
appeared, was from 5 to 6 grains. Hence it 
may be said, that 7 grains of sulphur com- 
bined with 5-| of oxygen ; but as the white 
fumes are oxidized inferior to sulphurous acid, 
it is most probable that sulphur requires its 
ovvn weight of oxygen nearly to form sul- 
phurous acid. In confirmation of this, it is 
observable, that no material change of bulk is 


effected in the gas by the combustion j and 
this is also remarked in the analogous com- 
bustion of cliarcoal. Thus, then, the specific 
gravity of suiphuroMs acid should exhibit a 
near approximation to twice that of oxygen, 
as it is found to do above. Now, as it would 
be contrary to all analogy, to suppose sul- 
phurous acid to consist of 1 atom of sulphur 
and 1 of oxygen, we must presume upon its 
being I of sulphur and 2 of oxygen ; and hence 
the weight of an atom of salphur will be 14 
times that of hydrogen. 

Another and more rigid proof of the consti- 
tution of sulphurous acid, we obtam from the 
combustion of sulphuretted hydrogen in Volta's 
eudiometer. This compound, it will be 
shewn, contains exactly its own bulk of hy- 
drogen ; the rest is sulphur : Their relative 
weights, as appears from the specific gravity, 
must be I to 14 nearly; novv^ when sulphu- 
retted hydrogen is exploded with plenty of 
oxygen over mercury, the whole of the last 
mentioned gas is converted into water and 
sulphurous acid ; it is found that 2 measures of 
the combustible gas combine vvith 3 measures 
of oxygen ; but 2 measures of hydrogen take 
1 measure of oxygen ; therefore, the sulphur 
takes the other 2 measures ; that is, the atom 
of sulphur requires 2 atoms of oxygen for its 


combustion, and that of hydrogen 1 atom of 
oxygen ; which gives the same constitution 
as that deduced above for sulphurous acid. 

The proportions of sulphur and oxygen in 
this acid, have been variously stated, mostly 
wide of the truth. We have one account that 
gives 85 sulphur and 15 oxygen. Dr. Thomson, 
in Nicholson's Journal, vol. 6, page 97, gives 
68 sulphur and 32 oxygen ; but in his Ap- 
pendix to the Sd edition of his Chemistry, he 
corrects the numbers to 53 sulphur and 47 
oxygen. Desormes and Clement say 59 sul- 
phur and 41 oxygen (ibid. vol. 17 — page 42). 
According to the preceding conclusions, if the 
atom of sulphur be stated at 14 ; then the pro- 
portion of sulphur to oxygen will be 60 sul- 
phur to 50 oxygen, or equal weights ; but if 
sulphur be denoted by 13, then sulphurous 
acid will consist of 48 sulphur and 52 oxygen 
per cent., which numbers I consider as the 
nearest approximation : the diameter of the 
elastic atom of sulphurous acid is rather less 
than that of hydrogen, as appears from the 
circumstance that 5 measures of the gas sa- 
turate 6 measures ot sulphuretted hydrogen, 
which last contain as many atoms as the like 
measures of hydrogen. On this account, the 
diameter of an atom of sulphurous acid may 


be denoted by .95, and the number of atoms 
in a given volume, to that of hydrogen in the 
same volume, will be as (5 to 5, or 120 to 100. 

3. Sulphuric Acid. 

The sulphuric acid of commerce, commonly 
known in this country by the name of oil of 
vitriol, is a transparent liquid of an unctuous 
feel, of the specific gravity 1.84, and very 
corrosive ; it acts powerfully on animal and 
vegetable substances, destroying their texture, 
and mostly turning them black. This acid 
was formerly obtained from green vitriol (sul- 
phate of iron) by distillation ; hence the name 
vitriolic acid. It is now commonly obtained 
by burning sulphur, mixed with a portion of 
nitre, (from -ith to -jVth of its weight) in leaden 
chambers ; sulpliuric acid is formed and drops 
down into water, which covers the floor of 
the chambers j this water, when charged suf- 
ficiently with acid, is drawn off, and subjected 
to evaporation till the acid is concenirated in a 
higher degree ; when it is put into glass retorts, 
and placed in a sand bath ; the weaker part of 
the acid is distilled into receivers, and the 
others concentrated nearly as much as is pos- 


sible in the circumstances. The acid in the 
receivers is again boiled down and treated as 

Some authors have affected to consider the 
theory of the formation of sulphuric acid as 
very obvious ; the nitre, they say, furnishes a 
part of the oxygen to the sulpliur, and the 
atmosphere supplies the rest. Unfortunately 
for this explanation, the nitre, if it were all 
oxygen, would not furnish above -^Vth of what 
is wanted ; but nitre is only 55 per cent, oxy- 
gen J it cannot, therefore, supply the sulphur 
with much more than V^th })art of wliat it 
wants, if all the oxygen were extricated ; but 
not more than ~ or 4-d of this small portion is 
disengaged from the potash ; for, the salt be- 
comes a sulphate instead of a nitrate, and re^ 
tains most of the oxygen it had, or acquires 
oxygen again from some source. Several well 
informed manufacturers, aware of the fallacy of 
the above explanation, have attempted to di- 
minish the nitre (which is an article of great 
expence to them), or to discard it altogether ; 
but they find it indispensibly necessary in some 
portion or other ; for, without it they obtain 
little but sulphurous acid, which is in great 
part incondensible, and not the acid they 
want. The manner in which the nitre operates, 
for a long time remained an aenigma. . At 


'length Desormtrs and Clement, two French 
chemists, have solved the difficulty, as may be 
seen in an excellent essay in the Anna], de 
Chimie, 180G, or in Nicholson's Journal, vol. 
17. These authors shew, that in the com- 
bustion of the usual mixture of sulphur and 
nitre, sulphurous acid is first formed, and ni- 
trous acid or nitrous gas liberated, partly from 
the heat, and partly perhaps from the action of 
sulphurous acid ; the nitrous gas or acid be- 
comes the agent in oxidizing the sulphurous 
acid, by transporting the oxygen of the atmo- 
spheric air to it, and then leaving them in 
union, which constitutes sulphuric acid. The 
particle of nitrous gas thert attaches another of 
oxygen to itself, and transports it to another 
atom of sulphurous acid ; and so on till the 
whole is oxidized. Thus the nitrous acid 
operates like a ferment, and without it no sul- 
phuric acid would be formed. 

This theory of the formatioii of sulphuric 
acid has so very imposing an aspect, that it 
scarcely requires experiment to prove it. It 
is, however, very easily proved by a direct 
and elegant experiment. Let 100 measures 
of sulphurous acid be put into a dry tube over 
mercury, to which add 60 of oxygen ; let then 
10 or 20 measures of nitrous gas be added to 
the mixture 3 in a few seconds, the inside of 


the tube beconnes covered with a crystalline 
appearances like hoar frost, and the mixture is 
reduced to ^d or ^th of its original volume. 
If now a drop of water be admitted, the crys- 
talline matter is quickly dissolved into the wa- 
ter, sparkling as it enters, and the gases en- 
tirely lose their elasticity, except a small resi- 
duum of azote and nitrous gas. If the tlibe is 
then washed out, the water tastes strongly acid, 
but has no smell of sulpharous acid. It is 
evident, that in this process the nitrous gas 
unites to the oxygen, and transports it to the 
sulphurous acid, which, receiving it from the 
nitrous, becomes sulphuric acid. It appears, 
moreover, that solid sulphuric acid is formed 
when no water is present ; and consequently 
this is the natural state of sulphuric acid en- 
tirely free from water. It must bft observed, 
that if any water in substance is present when 
the mixture of gases is made, the water seizes 
the nitrous acid as it is formed, and conse- 
quently prevents it oxidizing the sulphurous 
acid ; on the other hand, the presence of 
water seems necessary in the sequel, to take 
the new formed sulphuric acid away, in order 
to facilitate the oxidizement of the remaining 
sulphurous acid. The oxygen necessary to 
saturate 100 measures of sulphurous acid seems 
to be about 50 measures ; but it is difficult to 


ascertain this with precision, because the ni- 
trous gas takes up the superfluous oxygen, and 
begins to act upon the mercury. 

Now, it has been shewn, that sulphurous 
acid contains nearly its own bulk of oxygen, 
and is constituted of 1 atom of sulphur and 2 
of oxygen ; and it appears from the above, that 
half as much oxygen more, that is, 1 atom, 
converts it into sulphuric acid : hence, the 
sulphuric acid atom is constituted of 1 atom of 
sulphur and 3 of oxygen ; and if the atom of 
sulphur be estimated at 13 in weight, and 
the 3 of oxygen at 21, the whole compound 
atom will weigh 34 times the weight of an 
atom of hydrogen ; that is, pure sulphuric 
acid consists of 38 sulphur and 62 oxygen per 

In the year 1806, by a careful comparison 
of all the sulphates, the proportions of which 
are well known, I deduced the weight of the 
atom of sulphuric acid to be 34 ; it now ap- 
pears that the same weight is obtained syn- 
thetically, or without any reference to its 
combinations ; the perfect agreement of these 
deductions, renders it beyond doubt that the 
weight is nearly approximated, and confirms 
the composition of the atom which has just 
been stated. 

There are scarcely any chemical principles. 


the proportions of which have been so di- 
versely determined by experimentalists, as 
those of sulphuric acid : the following table 
will sufficiently prove the observation j ac- 
cording to 

Berthollet 72 sulphur 4- 28 oxygen. 

-f- 30 















+ 31 
+ 38.5 
+ 44.4 
+ 57,5 
+ 58 • 
+ 58 • 

Chenevix's result would have been 44- sul- 
phur + 56 oxygen, if he had adopted 33 per 
cent, acid in sulphate of barytes, which is 
now generally admitted. The method which 
be and the later experimentalists have taken, 
is to distil nitric acid from a given weight of 
sulphur, till the whole or some determined 
pari of the sulphur is converted into sulphuric 
acid; the acid is thea saturated wiih barytes, 
and the weight of the salt ascertained. 

Notwithstanding the above theory of the 
formation of sujphuric acid was such as to 
convince nie of its accuracy, I was desirous to 
see the manufacture of it on a large scale. 


and by th? generous invitation of Mr. Watkins, 
of Darcy Lever, near Bolton, I had lately an 
opportunity of gratifying myself by the in- 
spection of his large and well-conducted acid 
manufactory, near that place. When opening 
a small door of the leaden chambers, there is- 
sued a volume of red fumes into the air, which 
by their colour and smell, left no rooni to 
doubt of their beinnr the fumes of nitrous acid. 
There was scarcely any smell of sulphurous * 
acid. From the nitrous fumes, one would 
have been inclined to think that the chambers 
were filled with nitrous gas. I was particu- 
larly anxious to know the constitution of the 
air in the interior of the chambers, and Mr. 
Watkins was so obliging as to send me a 
number of phials of air taken from thence. 
Upon examination, the air was found to con- 
sist of 16 per cent, oxygen and 84 azote. 
There was no smell of sulphurous acid, and 
very little of nitrous acid, this last having 
been condensed in passing through the water. 
In fact, it seems that the nitrous acid fumes 
never make more, perhaps, than 1 per cent, 
upon the whole volume of air ; nor can the 
oxygen be ever reduced much below 16 per 
cent., because the combustion would instantly 
cease. A constant dropping is observed from 
the roof of the chambers internally ; these drops 


being collected, were found to be of the spe- 
cific gravity 1 .6 ; they had no sulphurous smell, 
but one slightly nitrous. 

It is not very easy to suggest any plausible 
alteration in the maaagement of a manufactory 
of this article.— Nitrou5 acid must be present ; 
but whether it is best obtained by exposing 
nitre to the burning sulphur, or by throwing 
in the vapour of nitrous acid by direct distil- 
lation, may be worth enquiry. Loss of nitrous 
acid is unavoidable, partly by its escape into 
the air during the periods of ventilation, and 
partly by its condensation in the watery acid, 
on the floors of the chambers ; a regular supply 
must, therefore, be provided ; but if this ex- 
ceed a certain quantity, it not only increases 
the expence, but is injurious to the sulphuric 
acid in some of its applications. There must, 
m all probability, be some figure of the cham- 
bers better than any other, in regard to their 
proportions as to length, breadth, and height ; 
this, perhaps, can be determined only by ex- 
perience. As water absorbs the nitrous acid 
with avidity, high chambers, and the com- 
bustion carried on at a distance from the water, 
must be circumstances favourable to economy 
in regard to nitre. 

Sulphuric acid has a strong attraction for 
water j it even takes it from the atmosphere 


in the state of steam, with great avidity, and 
is therefore frequently used in chemistry for 
what is called dryivg the air. When mixed 
with water, sulphuric acid produoes much 
heat, as has already been stated in the first 
part of this work. 

When sulphuric acid is boiled upon sul- 
phur, it has been said sulphurous acid is 
formed : I have not found this to be the case. 
But charcoal and phosphorus decompose the 
acid by heat ; and the results are carbonic acid, 
phosphoric acid, and sulphurous acid. 

Sulphuric acid combines with the alkalies 
and earths in general, forrhing with them 
salts denominated sulphates. On the metals 
this acid acts variously, according to its con- 
centration ; when diluted with 5 or 6 times its 
bulk of water, it acts violently on iron and 
zinc ; great quantities of hydrogen gas are 
produced, which proceed from the decompo- 
sition of the water, and the oxygen of the 
water unites with the metal, to which the acid 
also joins itself, and a sulphate is thus formed. 
When the acid is concentrated, its action on 
metals is less violent ; but by the assistance of 
iieat, it oxidizes most of them, and gives ofF 
sulphurous acid. 

As the sulphuric acid exists in various de- 
grees of concentration, it becomes a matter of 


importance both to its manufacturer, and to 
those who use it largely, as the dyers and 
bleachers, to know the exact strength of it ; 
or in other words, to know how much water 
is combined with tlie pure acid in any spe- 
cimen. This subject engaged the particular 
attention of Kirvvan some years ago, and he 
has furnished us with a table of the strengths 
of sulphuric acid, of most densities. There 
are two things requisite to form an accurate 
table, the one is to ascertain the exact quan- 
tity of real acid in some specimen of a given 
specific gravity ; the other is to observe care- 
fully the effects produced on the specitic gra- 
vity of such acid, by diluting it with a given 
<]uantity of water. Mr, Kirwan has succeeded 
very well in the former, but has been pecu- 
Jiarly unfortunate in the latter. The errors of 
his table seem to have been known for the last 
10 years to every one, except the editors oF 
works on chemistry. The following table 
exhibits the results of my own experience on 
this acid for several years. 



Table of the quantity of real acid in 100 parts of liquid 
sulphuric acid^ at the temperature 60". 

Add. Water. 


Acid per r^'nt. 
by wci{;ht. 


Acid per cent, 
by measure. 


Specific gra- 


Boiling point. 


1+ 1 








605 • 












































447 « 

1+ 2 






















J 08 















1+ 3 











1 .408 


1 + 10 
1 +17 





1 +38 





Remarks on the preceding Table. 

1. The acid of 81 per cent, is constituted of 
1 atom of acid and 1 of water. It is the 
strongest possible acid tfiat can be obtained by 
boiling the liquid acid ; because at that strength 


the acid and water distil together, in the same 
way as nitric acid of 1.42 sp. gravity, or mu- 
riatic of 1.094. It is a mistai^en notion, that 
the common sulphuric acid of commerce is of 
the maximum strength, though it is of the 
maximum density nearly. The fact is, acid 
nearly of the maximum strength varies very 
little in its specific gravity, by the addition or 
subtraction of a small quantity of water. Here 
is Kirwan's principal error. Acids of the 
strength of 81 and 80, do not differ more than 
1 in the third place of decimals ; whereas, ac- 
cording to his table, tlie difference is 14 times 
as great. The acid of commerce varies trom 
75 to 80 per cent, of acid, or about 7 per cent. 
in value, in the different specimens I have had 
occasion to examine. This variation only 
changes the second figure in decimals an unit i 
though, according to Kirwan's table, the 
change is 7 times as much. The specific gra- 
vity ought not to be the criterion of strength 
in acids above 70 per cent. ; the temperature 
at which they boil is a much better criterion, 
because it admits of a range of 12 or 15° for 1 
per cent, of acid. Or the strength may be 
found by determining what quantity of water 
must be added to reduce the acid to some 
known strength, as that of the glacial acid, 
of 1.78 sp. gravity. 

406 Oxygen with sulphur, 

2. There is nothing further striking In the 
table till we come to the aci'd, which is con- 
stituted of 1 atom to 2 of water ; this acid 
possesses the remarkable property of congealing 
in a temperature at or above 32% and of re- 
maining congealed in any temperature below 
46° ; its specific gravity is 1.78, as Keir found 
it, (Philos. Trans. 1787), and it contains 68 
per cent, of real acid, both by theory and ex- 
periment ; it is determined by theory thus : 
— one atom of sulphuric acid weighs 34, and 
2 of water 16, together making 50 j hence, if 
50 : 34 : : 100 : 68 ; it is found experimen- 
tally thus : let 100 grain measures of glacial 
sulphuric acid be saturated with carbonate of 
potashy and the sulphate of potash be ob- 
tained ; it will weigh, after being heated to a 
moderate red, nearly 270 grains, of which 
121 will be acid, and 149 alkali, according to 
the analyses of Kirwan and Wenzei. If the 
liquid acid be of greater or less specific gra- 
vity, so as to contain even 1 per cent, more or 
kss real acid, then it cannot be frozen in a 
temperature above 32% but may in a tempe- 
rature a little below 32°. If the liquid acid 
contain 3 per cent, more or less than the 
glacial, it cannot be frozen without the cold 
produced by a mixture of snow and salt ; and 
that is insufficient, if it deviate more than 3 


per cent, from the glacial, as Mr. Keir deter- 
mined. I find the frozen acid to be of the 
specific gravity 1.88 nearly. It seems pro- 
bable that the difficulty of freezing would in- 
crease in both sides, till the acids of 1 and 1 
above, and 1 and 3 below. 

3. The acids below 30 per cent, may, with- 
out any material error, have their strength 
estimated by the first and second figures of 
decimals in the column of sp. gravity j thus 
acid of 15 per cent, strength, will have the 
specific gravity 1.15, Sec. 



There are only two compounds of oxygen 
and phosphorus yet known : they both have 
the characters of acids ; the one is denomi- 
Tiated phosphorous acid, the other phosphoric 
acid. It is extremely probable that the former, 
though recognised as an acid, is yet in the 
lowest degree of oxidation, and may therefore 
with equal propriety be called phosphorous 
oxide, phosphoric oxide, or, after the manner 
of metals, oxide of phosphorus. We shall, 
however, adopt the common name. 


1. Phosphorous Acid. 

When phosphorus is exposed for some days 
to the atmosphere, it gradually acquires oxy- 
gen, and is converted into an acid liquid. 
This process may be effected by putting small 
pieces of phosphorus on the sloping sides of a 
glass funnel, and suffering the liquid to drop 
into a phial as it is formed. The liquid, called 
phosphorous acid, is viscid, tastes sour, and is 
capable of being diluted "with water to any 
amount. It has the usual effect of acids on the 
test colours. When heated, water is evapo- 
rated, and afterwards phosphuretted hydrogen 
gas ; finally, there remains phosphoric acid in 
the vessel. It should seem from this, that 
heat gives the oxygen of one part of the phos- 
phorous acid to another, by which the latter 
is changed into phosphoric acid, and the phos- 
phorus of the former is liberated ; but at that 
degree of heat the liberated phosphorus acts 
on the water ; one part of it takes the oxygen 
to form more phosphorous acid, and the other 
takes the hydrogen to form phosphuretted 
hydrogen ^ and thus the process is carried on 
till all the phosphorus is in the state of phos- 
phoric acid, or phosphuretted hydrogen. It 
is probable, that in this way the phosphorus 


is divided, so that two thirds of it are united 
to oxygen, and one third to hydrogen ; but 
this has not been ascertained by direct ex- 

Phosphorous acid acts upon several metals, 
oxidizing them by the decomposition of wa- 
ter, and at the same time giving out phosphu-. 
retted hydrogen ; the resulting metallic salts 
are, it is supposed, phosphates, the redundant 
phosphorus being carried off by the hydrogen. 
This acid combines with the alkalies, earths, 
and metallic oxides, and forms with them a 
class of salts called pJwsphitcs. 

When nitric acid is put to phosphorous acid, 
and heat applied, the nitric acid is decom- 
posed, half of its oxygen unites to the phos- 
phorous acid, and converts it into phosphoric 
acid, and the rest of the nitric acid escapes in 
the form of nitrous gas. 

The proportion of the two elements consti- 
tuting phosphorous acid has not hitherto been 
ascertained ; I am inclined to believe, from the 
experiments and observations about to be re- 
lated concerning phosphoric acid, that phos- 
phorous acid is composed of 1 atom of phos- 
phorus, weighing 9 nearly, and 1 of oxygen, 
weighing 7 ; the compound weighing 16. If 
this be the case, it may appear singular that 
none of the other elements exhibit acid pro- 


parties when combined with 1 atom of oxy- 
gen ; but it should be observed, that the phos- 
phoric oxide is in a liquid form, and disposed 
to separate into phosphorus and phosphoric 
acid, circumstances that do not combine in 
regard to the other oxides. In fact, phos- 
pherous acid may be considered as phosphoric 
acid holding phosphorus in solution, rather 
than as a distinct acid. 

2. Phosphoric Acid. 

Though some of the compounds of phos- 
phoric acid, and the earths and alkalies, are 
common enough, yet this acid, in a pure 
state, is rarely obtained in any considerable 
quantity, requiring a process both tedious and 
expensive. There are three methods by which 
phosphoric acid may be formed : 1. If a small 
portion of phosphorus, namely, from 5 to 20 
grains, be ignited, and immediately covered 
with a large bell glass, over water, the phos- 
phorus burns with great brilliancy, and soon 
fills the vessel with white fumes ; in a short 
time, the combustion ceases ; after which the 
fumes gradually subside, or adhere to the side 
of the glass in the form of dew ; these white 
fumes are pure phosphoric acid. 2. If a small 


piece of phosphorus be dropped into heated 
nitric acid in a phial or gas bottle, a brisk 
effervescence ensues, occasioned by the escape 
of nitrous gas, and the phosphorus gradually 
disappears, being converted into phosphoric 
acid, and mixed with the remaining nitric 
acid ; another small piece may then be dropped 
into the liquid, and so on in succession till 
the nitric acid is almost wholly decomposed ; 
the remaining liquid may then be gradually 
increased in temperature, to drive off all the 
nitric acid ; what is left is a liquid consisting 
of phosphoric acid and water ; by increasing 
the heat to a moderate red, the water is driven 
off, and liquid phosphoric acid remains, which 
on cooliflg becomes like glass. 3. If phospho- 
rous acid be prepared by the slow combustion 
of phosphorus, as mentioned above, and then 
a portion of nitric acid added to the liquid, 
and heat be applied, the nitric acid gives part 
of its oxygen to the phosphorous acid, and 
nitrous gas escapes. What remains, when 
heated, is pure phosphoric acid. 

Of these three processes, the first may be 
recommended when the object is to find the 
proportion of the elements of the acid ; but the 
second and third, when the object is to pro- 
cure a quantity of acid for the purposes of in- 
vestigation. Of these the third is preferable 


in an economical point of view, because rt 
requires only half as much nitric acid. By 
calculation, I find that 20 grains of phos- 
phorus will require '200 grains of nitric acid 
of 1.35, by the second process, but only 100 
grains by the third ; but a small excess 
should always be allowed for loss by evapo- 
ration, &:c. 

Phosphoric acid, in the state of glass, is de- 
liquescent when exposed to the air ; it be- 
comes oily, and may be diluted with any 
quantity of water. This acid is not so cor- 
rosive as some others ; but it has the other 
acid properties of a sour taste, of reddening 
vegetable blues, and of combining with the 
alkalies, earths, and metallic oxides, to form 
salts, which are called phosphates. It has the 
power of oxidizing certain metals, by decom- 
posing water in the manner of sulphuric acid ; 
the oxygen of the water unites to the metal, 
and the hydrogen is liberated in the state of 
gas. Charcoal decomposes this acid, as well 
as the phosphorous, in a red heat ; hence the 
process for obtaining phosphorus form super- 
phosphate of lime. 

Nothing very certain has been determined 
respecting the relation of the strength of this 
acid to the specific gravity of the liquid solu- 
tion. Some experience I have had, makes me 


think the following table will be found nearly 
correct : at all events, it may have its use till 
a better can be formed. 

Table of the quantity of real acid In 100 parts 
of liquid phosphoric acid. 

Acid per cent, 
by weight. 

Acid per cent, 
by measure. 

Specific gravity 
















Lavoisier ascertained the relative weights of 
phosphorus and oxygen in phosphoric acid to 
be 40 to 60 nearly : this was effected by burn- 
ing phosphorus in oxygenous gas. This im- 
portant fact has been since corroborated by 
the experience of others. I find a near ap- 
proximation to this result by burning phos- 
phorus in atmospheric air. In a bell glass, 
containing 400 cubic inches of air, 5 grains of 
phosphorus were repeatedly burnt over water ; 
the combustion at first was very vivid, but 
towards the conclusion it was languid ; there 
was a residuum of moist, half burned phos- 
phorus in the cup, usually about 1 grain : the 
glass had a flaccid bladder adapted to it to 
receive the rarefied air, so as to suffer none to 


escape. The air at first contained 20| per 
cent, oxygen j but after the combustion, it 
contained only 16 or \6^ per cent., the tem- 
perature being about 40° at the time. Whence, 
by calculation, it appears that in these in- 
stances !• grains of phosphorus may be con- 
cluded to have united to 6 grains of oxygen. 
The data, indeed, would give a rather less 
proportion of ^oxygen ; but it is probable that 
some phosphorous acid is formed near the con- 
clusion of the combustion. 

With respect to the constitution of the phos- 
phoric acid atom, there can be but two opi- 
nions entertained. Either it must be 1 atom 
of phosphorus with 2 atoms of oxygen, or 
with 3 of oxygen. According to the former 
opinion, the phosphoric atom will weigh 9, 
and the phosphoric acid atom 23 ; according 
to the latter opinion, the phosphoric atom will 
weigh 1 J-, and the acid atom 35. We might 
appeal to the phosphates to determine the 
weight of the acid ; but this class of salts has 
not been analyzed wiih sufficient precision. 
Fortunately, there is another compound of 
phosphorus which is subservient to our pur- 
pose ; namely, phosphuretted hydrogen. As 
the properties of this gas will be treated of in 
the proper place, we shall only observe here 
^hat the gas is a compound of phosphorus and 


hydrogen j that it contains just its bulk of 
hydrogen ; that its specific gravity is about 10 
times that of hydrogen ; and that when fired 
in Volta's eudiometer along with oxygen, it is 
converted into water and phosphoric acid, 
requiring 150 percent, in volume of oxygen 
for its complete combustion j but is, notwith- 
standing, burnt so far as to lose its elasticity 
with 100 measures of oxygen. These facts 
leave no doubt that the atom of phosphorus 
weighs 9 ; that the atom of phosphoric acid 
weighs 23, being a compound of 1 with 2 of 
oxygen ; that the atom of phosphorous acid 
is 1 with 1 of oxygen, weighing 16, and that 
phosphorous acid and water are formed when 
equal volumes of phosphuretted hydrogen and 
oxygen are exploded together. 



Only one compound of hydrogen and azote 
has yet been discovered : it has been long 
known to chemists as an important element, 
and under various names, according to the 
state in which it was exhibited, or to the ar- 
licle from which it was derived j namely, vo- 


latilc alkaliy hartslwriiy spirit of sal ammo- 
niaCy &c. but authors at present generally dis- 
tinguish it by the name of ammonia. Its nature 
and properties we shall now describe. 


In order to procure ammonia, let one ounce 
of powdered sal ammoniac be well mixed with 
two ounces of hydrate of lime (dry slaked 
lime), and the mixture be put into a gas 
bottle i apply the heat of a lamp or candle, 
and a gas comes over, which must be received 
in jars over dry mercury, li; is dmmoniacal 
gaSy or ammonia in a pure state. 

This gas is unfit for respiration, and for sup- 
porting combustion ; it has an extremely pun- 
gent smell, but when diluted with common 
air, it forms an useful and well-known stimu- 
lant to prevent fainting. The specific gravity 
of this gas has been found nearly the same 
by various authors, which is the more remark- 
able, as the experiment is attended with some 
difficulties that do, not occur in many other 
cases. According to Davy, 100 cubic inches 
of it weigh 18. grains; according to Kirwan, 
18.2 grains j Allen and Pepys, 18.7; and 
Biot, 19.6; the mean of these, 18.6 grains, 


may be considered as a near approximation at 
the temperature 60" and pressure 30 inches of 
mercury : hence the specific gravity is .6, the 
weight of atmospheric air being one. 

Ammoniacal gas sent into water, is con- 
densed almost with the same rapidity as steam ; 
in this respect it corresponds with fluoric and 
muriatic acid gases. The compound of water 
and ammonia forms the common liquid am- 
monia sold by the name of spirit of sal ammo- 
niac ; this is the form in which ammonia is 
the most frequently used. It. is of great im- 
portance to ascertain the quantity of gaseous 
or real ammonia in given solutions of ammonia 
in water. This subject has been greatly neg- 
lected ; a very good attempt was made about 
10 years ago by Mr. Davy, to ascertain the 
quantity of ammonia in watery solutions, of 
different specific gravities ; the result was a 
table, which may be considered an excellent 
first approximation ; hut it is to be regretted 
that so important an enquiry should not have 
attracted attention since. I have instituted a 
few experiments on this head, the results of 
which will no doubt be acceptable. 

A phial, capable of holding 1400 grains ot 
water, was partly filled with mercury, and the 
rest with 200 grains of water, and inverted in 
mercury ; into this 6000 grain measures of am* 


moniacal gas were transferred ; the liquid had 
not diminished sensibly in specific gravity ; 
it required 2'!-^ grain measures of muriatic 
acid, 1.155, to saturate the water; by evapo- 
rating in a heat below boiling water, 12 grains 
of dry muriate of ammonia were obtained. 
!Novv, supposing 1400 measures of gas equal 
to 1 grain in weight, there would be found in 
the salt 5.7 grains of muriatic acid, 4.3 grains 
of ammonia, and 2 grains of water. I found 
this method of proceeding not to be relied 
upon ; for, though the mercury had recently 
been dried in an oven in the temperature 240", 
yet the ammoniacal gas could not be trans- 
terred from one graduated tube to another, 
without a loss of 10 or 15 per cent. ; I had 
reason to conclude, then, that the ammonia 
jn the above salt was overrated. In order to 
avoid this source of error, I adopted the method 
first used by Dr. Priestley, of putting muriatic 
acid gas to the alkaline in the graduated tube ; 
but here was still an objection, as the muriatic 
acid gas must be measured previously to the 
transfer, and it is equally absorbable by water 
with alkaline gas. However, I found, as Dr. 
Priestley had done before, that equal measures 
of the two gases as nearly as possible saturated 
each other. For, when a measure of acid gas 
was put to one of alkaline, there was a small 


residuum of alkaline gas ; and when the alka- 
line was transferred to the acid, there was a 
small residuum of acid gas. Having before 
concluded (page 287) that muriatic acid gas 
was of the specific gravity 1.61, 1 might have 
adopted the ratio of acid and alkali in muriate 
of ammonia to be 1.61 to .6 ; and hence have 
inferred the quantity and volume of ammonia 
in a given solution, from the quantity of mu- 
riatic acid solution requisite to saturate it. 
But there was one important circumstance 
against this ; the atom of muriatic acid I knew 
weighed 22, and the ratio of 1 .61 to .6, is the 
same as 22 to 8.2 nearly ; hence, the weight 
of an atom of ammonia must have been 8.2 or 
4.1, which. I was aware was inconsistent with 
the previous determinations concerning azote 
and hydrogen. Observing in the 2d vol. of 
of the Mcmoirta (TArcueiL that Biot and Gav 
l^ussac find the specific gravity of muriatic 
acid gas to be so low as 1.278, and under- 
standing from conversation with Mr. Davy, 
that he also had found the specific gravity of 
the gas to be considerably-less than I had con- 
cluded, I was induced to repeat the experi- 
ment of weighing it, taking every care to 
avoid the introduction of liquid solution. X 
ient a streatn of acid gas, derived from com- 
jnon salt and concentrated sulphuric acid, 


through an intermediate vessel, into a dry flask 
of common air, loosely corked, till it had ex- 
pelled 4ths of the air, as appeared afterwards; 
the inside of the glass had a very slight opacity 
on its surface ; it had gained l-j-V grain in 
weight ; it was then uncorked and its mouth 
plunged into water, when |ths of the flask 
were in a few moments occupied by the water. 
Other trials gave similar results. The flask 
held 6 grains of common air. Whence I de- 
rive the specific gravity of muriatic acid gas to 
be 1.23, and am induced to apprehend that 
this is rather more than less than the truth. 
The weights of equal volumes of muriatic acid 
gas and ammoniacal gas will then be as 1.23 
to .6; or as 22 to 11, nearly; and if we as- 
sume that 11 measures of acid gas are sufficient 
for 12 of alkaline, which is not unlikely from 
experience ; then we shall have 22 parts acid 
to 12 of ammonia for the constitution of mu- 
riate of ammonia (exclusive of water), which 
will make the theory and experience har- 
monize ; according to this view, muriate of 
ammonia must consist of 1 atom of muriatic 
acid and 2 of ammonia, each atom of ammo- 
nia being a compound of 1 atom of azote and 
1 of hydrogen. However this may be, I find 
that 22 parts of real muriatic acid, 38 of nitric, 
and Z'h of sulphuric, as determined by the re- 



spectlve foregoing tables, will saturate equal 
portions of any ammoniacal solution ; these, 
then, may be considered as tests of the quan- 
tity of real ammonia in different solutions ; 
and if the ratio of 22 to 12, above adopted, 
be incorrect, it cannot be greatly so ; and the 
error will be general, being so much per cent, 
upon any table of ammoniacal solutions. The 
test acids I prefer for use, are such as contain 
half the quantities of acid above stated in 100 
grain measures. Thus, 100 grain measures 
of muriatic acid, sp. gravity 1.074, contain 
1 1 grains of real acid ; 100 measures of nitric 
acid, 1.141, contain 19 grains; and 100 mea- 
sures of sulphuric acid, 1.135, contain 17 
grains of real acid. Now, 100 measures of 
ammoniacal solution of .97 sp. gravity, are 
just sufficient to saturate these. Whence I 
adopt that solution as test ammonia, and con- 
clude that 100 grain measures of it contain 6 
grains of real ammonia. 

It will be perceived, then, that the accuracy 
of the ensuing table depends upon several 
points: namely, whether 100 measures of mu- 
riatic acid of 1.074, really contain 11 grains 
of acid ; whether the specific gravities of mu- 
riatic acid gas, and ammoniacal gas, are really 
1.23 and .6, or in that ratio ; and whether 11 
measuxes of acid gas saturate 12 measures of 



ammoniacal gas. I believe the errors in any 
of these particulars to be very small, and pro- 
bably they may be such as partly to correct 
each other. 

I find, after Mr, Davy, that a measure of 
water being put to a measure of ammoniacal so- 
lution, the two occupy two measures, without 
any sensible condensation ; consequently, if the 
quantity of ammonia in a measure of any given 
specific gravity, as .90, be determined ; then 
the quantity in a measure of .95, will be just half 
as much : Hence, a table is easily constructed 
tor measures, and one for weights is derivable 
without much calculation. 

Table of the t]Manlitics of real or gaseous ammonia in so- 
lutions of different specific gravities. 

Sprtific gr»- 

Grains of aimno- 

Cr.iint of ammo- 

Boiling pbint 

Volume of g»5 


Ti\A in ICO water 

nia in loo grains 

of tlic liquid 

coiidtfnsed in a 

gram measures 

of liquid. 

given volume ul 

of litjuid* 

old scale. 























2 'J 





















15 1 





12 8 










8 3 



















On ihe above table, it jnay be oroper to re- 
mark, that I have not had large quantities of 
ammonlacal solution lower than ,94, so as to 
find their specific gravities experinientally ; 
but have had small quantities to the amount of 
10 or 20 grains of the several solutions from 
26 to 12 per cent. ; I have no reason to sus* 
pcct any material deviation from the law of 
descent observed in the specific gravity down 
to 12 per cent., when we go below that num- 
ber ; at all events, it cannot be great down 
to .85, and it is not of much importance, be- 
cause solutions of that strength arc never ob- 
tained in the large way. — The second column, 
exhibiting the grains of ammonia in 100 mea- 
sures of the solution, is more convenient for 
practice than the third, which gives the 
weight in 100 grains of solution. I'he fourth 
column, vvhich shews the temperature at 
which the several solutions boil, will be found 
highly interesting. The ebullition of a liquid 
is well Icnown to take place, when the steam 
or vapour from it is of the same force as the 
atmospheric pressure. In solutions down to 
12 per cent., the experiments were performed 
by inserting a thermometer into a phial con^ 
taining the solution, and plunging the phial 
into hot water till the liquid boiled 5 but in 
the higher solutions a small portion, as 20 


grains, was thrown up a tube filled with mer- 
cury ; the tube was then put into a phial of 
mercury, and the whole plunged into warm 
water ; the temperature was then ascertained 
requisite to bring the mercury in the tube to 
the level of that in the phial. The fifth co- 
lumn is calculated from the second, sup- 
posing the specific gravity of ammoniacal gas 
= .6. 

It may be observed, that the above table 
gives the quantity of ammonia in different so- 
lutions, from 15 to 20 per cent, less than Mr. 
Davy's table ; also, that the common ammo- 
niacal solutions of the shops usually contain 
from 6 to 12 per cent, of ammonia. 

Before we can estimate the value of the 
fourth and fifth columns of the table, we must 
ascertain the force of vapour from ammoniacal 
solutions at different temperatures. If it be 
found in some one instance, we may by ana- 
logy infer the results in others. As the steam 
from water varies in force in geometrical pro- 
gression to equal increments of temperature, 
it might be expected that the steam or gas 
from liquid ammonia should do the same ; but 
as the liquid is a compound, the simple law 
of the force of aqueous steam does not obtain. 
It appears, however, from the following re- 
sults, that a near approximation to this law is 



observed. Into a syphon barometer I threw 
a quantity of .946 liquid ammonia, which 
was by agitation, &c. transferred to the va- 
cuum over the mercury. The vacuum was 
then immersed successively in water of different 
temperatures, and the force of the gas observed 
as under, 


Force of atnraonl* 
old scale, new scale. diiFcrences. acai gteani fiom 

liquid .946. 

140" 15 r 30 inch, 

103' 115» J 5 

74" 84*" 7.5 

50^ 55° 3.75 

Hence it seems, that the intervals of tempe- 
rature required to double the force of ammo- 
niacal steam, increase in ascendinp^. I had 
no doubt but this sort of steam or gas, would 
mix with common air, without having its elas- 
ticity affected, like as other steams do ; but 1 
ascertained the fact by experiment : Thus I 
mixed a given volume of air with steam of 15 
inches force, and found that the air was doubled 
in bulk. 

These facts are curious and important. They 
shew that ammonia is not retained in water 


without external force, and that the pressure 
of no elastic fluid avails but that of ammo- 
niacal gas itself ; thus establishing the truth of 
the general law which I have so much insisted 
on, that 710 elastic fluid is a sufficient barrier 
agai?ist the passage of another elastic fluid. 

We may now see upon what causes the 
saturation of water with ammonia depends. 
They are two ; the temperature of the liquid ; 
end the pressure o^ihe incumbent ammoniacal 
gas, exclusive of the air intermixed with it. 
For instance, if the temperature be given, 50° 
(old scale) j then the strongest possible solu- 
tion, under atmospheric pressure, will be such, 
that 100 measures will have the specific gravity 
.87, and contain 26 grains of ammonia, or 
419 times the volume of gas. But if, in satu- 
rating the water by sending up gas, there be 
common air, so as to make |ths of the in- 
cumbent gas, then the solution cannot be made 
stronger than .946, of which 100 measures 
contain 11 grains of ammonia, or 162 times 
the volume of gas. I have obtained a satu- 
rated solution containing 26 per cent, ammo- 
nia, with TT^h common air in the incumbent 
gas J and at the same temperature, another 
saturated solution, containing only 17 percent. 
ammonia, with iths common air in the in- 
cumbent gas. 


With respect to the constitution of ammonia, 
Priestley, Scheele, and Bergman pointed out 
the t'.vo elements into whicii it is decomposed. 
Berthollet first settled the proportions of the 
elements, and the quantity of each obtained 
from a given volume of ammoniacal gas. It 
is highly to his credit too, that subsequent 
repetitions of his experiments, under the im- 
proved state of knowledge, liave scarcely 
amended his results. Priestley resolved 1 mea- 
sure of ammoniacal gas, by electricity, into 3 
measures of gas not absorbable by water ; but 
his ammonia could not have been dry. Ber- 
thollet resolved 17 measures into 33 in tlie 
same way : this result has since been corro- 
borated by various authors. He also found 
that the gas so produced, was a mixture of 121 
parts of azote by weight, with 29 of hydrogen ; 
or 4.^^ azote with 1 of hydrogen. 

In 1800, Mr. Davy published his researches, 
in which were given several interesting results 
on ammonia, Mr. Davy decomposed ammo- 
nia, by sending the gas through a red hot 
po:celain tube ; after the common air was ex- 
pelled, the collected gas was found free from; 
oxygen. To 140 measures of this gas were 
added 120 of oxygen ; the mixture being ex- 
ploded by electricity, 1 10 measures of gas were 
left; and of course 150 were cenverted intv' 


water ; of this 100 measures must have been 
hydrogen. Whence, 140 measures of the ga$ 
from decomposed ammonia, contained 100 hy- 
drogen and 40 azote j or 100 measures con- 
tained 71.4 hydrogen and 28.6 azote. This 
conclusion was so nearly agreeing with the 
previous determination of Berthollet, that both 
have justly been held up as specimens of the 
accuracy of modern chemical analysis. 

In 1808, Mr. Davy published his celebrated 
discoveries relating to the decomposition of 
the fixed alkalies. Having ascertained that 
these contained oxygen, he was led by analogy 
to suspect the same element in ammonia. Se- 
veral experiments were made, which seemed 
to countenance this idea ; but these could not 
be considered conclusive, as long as it was ad- 
mitted that no oxygen appeared in the decom- 
position of ammonia by electricity, and yet 
that the weight of the azote and hydrogen 
were together equal to that of the ammonia 
decomposed. Mr. Davy re-examined the spe- 
cific gravity of ammoniacal gas, the quantity 
of gaseii evolved by the decomposition of a 
given volume of it, and the ratio of azote to 
hydrogen in the same. The result was, that 
the gases obtained amounted only to -j-Tths of 
the weight of the arhmonia ; the remaining 
^Vth Mr. Davy thought must be oxygen. 


which, uniting to hydrogen, formed a portion 
of water. The way in which this ^[h was 
saved, was principally by diminishing the ab- 
solute quantity of gases derived from a given 
volume of ammonia, but partly by finding less 
azote and more hydrogen than had been before 
estimated. Thus, 100 measures of ammo- 
niacal gas produced only 180 measures of 
mixed gas, though commonly estimated at 200; 
and this gas was found to consist of 26 azote 
and 74 hydrogen per cent. 

These conclusions, so different from what 
had been long adopted, and depending upon 
experiments of s^me delicacy, were not likely 
to be received without a more general scrutiny. 
Dr Henry in England, and A. B. BerthoUet 
in France, seem both to have renewed the 
investigation into the component parts of am- 
monia with great care and assiduity. Dr. 
Heniy's object was to determine whether any 
oxygen, water, or any other compound con- 
taining oxygen, could be detected in the ana- 
lysis of ammonia ; this enquiry included the 
two others; aamely^ the quantity of gases ob- 
tained from a given volume of ammoniacal 
gas, and the proportion of azore to hydrogen 
in the same. The results were, that neither 
oxygen nor water could be found ; that for the 
most part the bulk of ammonia was doubled 


by decomposition, even when the gas was 
previously dried with extreme care 3 and that 
the ratio of azote to hydrogen in the mixture, 
from an average of six careful experiments, 
was 27:1: to 72i-. In this last decision. Dr. 
Henry was so fortunate as to discover a more 
easy and expeditious mode of analysis than 
had been known before ; he found that am- 
moniacal gas mixed with a due proportion of 
oxygen, of nitrous oxide, or even of nitrous 
gas, would explode by an electric spark. He 
found an under proportion of oxygen gas to 
answer best (about 6 measures of oxygen to 10 
of ammonia) : the explosion produced a com- 
pJete decomposition of the ammonia, and a 
partial combustion of the hydrogen ; after 
■which more oxygen was put to the residuum, 
and the remainder of the hydrogen consumed. 
From one experiment, in which 100 measures 
of ammonia were decomposed in a tube of 
which the mercury had been previously boiled. 
Dr. Henry only obtained 181 measures of gas j 
and he seems to think that this experiment 
may be the most correct in regard to that 
object. (Philos. Trans. 1809). 

In the Memoires d'Arcueil, tom. 2, M. A. 
B. BertholJet has a paper on the analysis of 
ammonia. He alludes to the experiments ot 
Berthollet in the memoirs of the academy. 


1785 J in which the ratio of 27.5 azote to 72.5 
hydrogen, was found in the decomposed aav 
tnonia, allowing 196 hydrogen for 100 oxygen. 
He repKDrts several experiments and observa- 
tions relative to the oxidation and deoxidation 
of iron in ammoniacal gas. He then proceeds 
to prove, that the weight of azote and hydro- 
gen produced in the decomposition of am- 
monia, is equal to the weight of the ammonia 
itself. Biot and Arago determine the specific 
gravities of azote, hydrogen^ and ammonia, 
to be .969, .078, and .597 respectively, which 
A. B. Berthollet adopts. He finds that 100 
measures of ammonia produce 205 of perma- 
nent gas ; which, by analysis^ gives 24.5 azote 
and 75.5 hydrogen per cent. Like Dr. Henry, 
A. B. Berthollet decomposed ammonia by ex- 
ploding it with oxygen gas ; but unfortunately 
he used an excess of oxygen, and then oeter- 
mlned the residuary oxygen by the addition of 
hydrogen : he was aware, however, that part 
of the azote was thus converted into nitric 
acid. Upon collecting the results, he makes 
it appear, that the gases produced by the de- 
composition of ammonia are, as nearly as pos- 
sible, equal to the weight of the ammonia. 

Though the experiments of these two au- 
thors may be deemed satisfactory, with regard 
to the non-existence of oxygen in ammonia. 


they would have been more so if they had 
accorded in the quantity of gas derived from a 
given volume of ammonia, and in the ratio of 
azote to hydrogen. Having made some expe- 
riments myself on these heads, I may be al- 
lowed to give my opinion as to the causes of 
these differences. — 1 am persuaded, with Mr. 
Davy, that ammonia is not doubled by decom- 
position, when due care is taken to prevent 
any liquid from adhering to the tube or mer- 
cury ; but at the same time am inclined to 
believe, from experience, that 100 measures 
of ammonia will give not less than 185 or 190 
measures of gas by dscomposition : I took a 
tube and filled it with dried mercury j then 
transferred a portion of gas into it, and by 
pushing a glass rod up the tube several times, 
displaced the mercury in the tube, so that no 
liquid ammonia could exist in the renovated 
mercury. This gas, being decomposed by 
electricity, produced after the rate of 1 87 for 
100. With respect to the ratio of azote to 
hydrogen, I am convinced it is to be obtained 
only by decomposing the ammonia previously 
to the combustion of the hydrogen, and this 
may be done either by electricity or by heat ; 
in these cases, ammonia will be resolved into 
28 measures of azotic gas, and 72 measures of 
hydrogen gas, in the hundred. I have re- 


peatedly obtained it so by electricity, the re* 
suits never deviating farther than from 27 to 
29 of azote. This agrees su^ciently with 
Berthollet's original analysis by electricity, 
and with Davy's analysis by heat in 1800; 
both of them made without any theoretic 
views as to quantity, wh'ch cannot be said of 
any of the subsequent investigations on this 

We are now to see how far these results 
will agree with the specific gravity of ammo- 
niacal gas : that is, whether the weights of the 
two gases are equal to the weight of the am- 
monia decomposed. 

100 measures of ammonia, which X sp. gr. .6 gives 60 
become 185 measures of mixed gas, _^^_ 

namely, 5I. 8 azote, — — — which X sp- gr. .967 gives 50.09 
and 133.* hydrogen, ~ — which X sp gr. .0? gives 10.65 


The excess of |ths of a giain upon 60, is too 
small to merit notice, and may arise from an 
inaccuracy in any of the data, which, if cor- 
rected, could have no material influence on the 

I shall now make a few observations on the 
other methods of analyzing ammonia. Dr, 
Henry's methods of burning ammonia in 
Volta's eudiometer along with oxygenous gas. 


nitrous gas, and nitrous oxide, unite elegance 
with expedition, and when well understood, 
cannot but be valuable. It appears to me, 
however, both from experience and analogy, 
that a compound combustible, such as am- 
monia, is never decomposed and one of its 
elements burnt, to the entire exclusion of the 
other. Numerous instances may be found in 
the compounds of charcoal and hydrogen, of 
phosphorus and hydrogen, &c. where one of 
the elements seizes the oxygen with more ra- 
pidity than the other ; but some portion of the 
other is always burnt. Even when the com- 
bustible gases are only mixed together, and 
not combined, we do not find that one of them 
precludes the other from taking a share of ♦he 
oxygen till it is saturated. Thus, in a mixture 
of carbonic oxide with hydrogen, witn a defi- 
ciency of oxygen, part of both is burnt by an 
electric spark. Dr. Henry has, indeed, no- 
ticed that ammonia fired with excess of oxy- 
gen, gives nitric acid as well as water. I have 
reason to believe this is the case in some de- 
gree, in whatever proportion they are fired, 
I have seldom obtained so much as 27 per 
cent, of azote by the combustion of ammonia 
with oxygen 'the hydrogen being estimated by 
doubling the oxygen spent), and in no in- 
stance 28 : but h will be manifest that all th« 


oxygen is not consumed in burning the hydro- 
gen, if we note the ammoniacal gas expended, 
and allow only 66 or 67 per cent, oxygen for 
the hydrogen ; there will generally be fnund a 
greater expence of oxygen, which must have 
gone to form nitric acid. The combustion of 
ammonia with nitrous gas usually gives from 
25 to 27 per cent, of azote, allowing the con- 
stitution of nitrous gas to be what is stated at 
page 331. Upon the whole, 1 fourtd nitrous 
oxide to approximate nearest to the truth. 
When 100 measures of ammonia are exploded 
with 120 of nitrous oxide, the gases resulting 
are azote with a very small portion of hydro- 
gen ; if to this a little hydrogen be added, and 
then an excess of oxygen, another explosion 
will determine the residuary hydrogen ; which 
being deducted, there remain about 172 azote, 
120 of which come from the nitrous oxide, 
and 52 from the ammonia, which gives after 
the rate of 28 azotf per cent, on the evolved 
gases. — When the decomposition of arrmonia 
is attempted by oxymuriatic acid gas, a gra- 
duated tube is filled wi.:h the gas, and plunged 
into liquid ammonia in this w^y, if we 
reckon a measure of the acid gas to a measure 
of hydrogen, we shall find the azote evolved 
and left in the tube, amount to 23 or 24 per 
cent, upon both gases. It is to be presumed. 


then, tha» oxymuriatic acid, like oxygen, 
consumes part of both the elements of am- 

By comparing the weight of azote with that 
of hydrogen in the above table, we find them 
as 4.7 to 1 nearly. This evidently marks the 
constitution of ammonia to be that of I atom of 
each of the elements combined. But we have 
before determined the element of azote to 
weigh 5.1, when treating of the compounds of 
azote and oxygen. This difference is probably 
to be ascribed to our having over-rated the 
specific gravity of nitrous gas, and perhaps 
nitrous oxide. In the Memoires d'Arciceil^ I 
observe Berard finds the specific gravity of ni- 
trous gas to be 1.04, instead of 1.10, which 
last I have made my calculations from ; if the 
former should prove true, it will reduce my 
valuation of azote in nitric acid nearly to 4.7 ; 
I have not had an opportunity of ascertaining 
the specific gravity of nitrous gas ; but am in- 
clined to believe that 1.10 may be too high. 
Berthollet finds nitrous oxide to be 1.36, in- 
stead of 1.61 i I much suspect the former is too 

Upon the whole, we may conclude that an 
atom of ammonia is constituted of 1 atom of 
hydrogen and 1 of azote, and weighs nearly 6. 
Thc diameter of the elastic particle is .909, 


that of hydrogen being 1. Or, 300 measures 
of ammoniacal gas contain as many atoms as 
400 measures of hydrogen, or as 200 of 



There are two combinations of hydrogen 
with carbone, now well known, easily dis- 
tinguishable from each other and from all other 
combinations. They are both elasHc fluids ; 
one of them, called olcfiant gas, is a compound 
of 1 atom of hydrogen and 1 of carbone ; the 
other, which I call carburetted hydrogen, is 
a compound of 2 atoms of hydrogen and I 
of carbone, as will be manifest f'-om what 

1 . Olefiafit Gas. 

The gas denominated oUfiant, was disco- 
vered and examined by t'ie Dutch chemists, 
Bondt, Dieman, &:c. and a memoir on the sub- 
ject was published in the loth vol. of the Jour- 
nal de Physique, 1794. 


defiant gas may be procured by mixing 2 
measures of sulphuric acid witli 1 measure of 
alcohal ; this mixture in a gas bottle must be 
heated to about 300" by a lamp, when the 
liquid exhibits the appearance of ebuHitioa, 
and the gas comes over : it should be passed 
through water, to absorb any sulphurous acid 
which may be generated. 

This gas is unfrt for respiration, and extin- 
guishes flame, but it is highly combustible : 
its specific gravity, according to the Dutch 
chemists, is .905 j according to Dr. Henry, 
.967. Perhaps .95 is abaut the truth. Water 
absorbs -^th of its bulk of this gas ; or the atoms 
of gas in the water are just twice the distance 
they are without j. and it may be expelled 
again by the othe" gases. This property (of 
being absorbed by' 8 times its bulk of water) 
occurred to me in ISOi, in a course of expe- 
riments on the absorption of gases by water. 
It is peculiar to this gas, and consequently 
distinguishes it from all others. When olefiant 
gas is mixed with oxymuriatie acid gas, a di- 
minution takes place, like as when oxygen 
and nitrous gas are mixed ; but the result is 
An oily which swims on the surface of the 
water. Hence the Dutch chemists gave this 
gas the name of olefiant. For this purpose, 
they found 3 measures of olefiant gas required 


4 measures of the acid gas j but Dr. Henry 
finds 5 of olefiant require 6 of the acid. The 
difference is not great, considering the diffi- 
culty of the experiment. As neither of these 
results will agree with the other known pro- 
perties of these two gases, I suspected that 
both would be found in some degree incorrect; 
which proved to be the case from the follow- 
ing experiments. Having taken two similar 
tubes graduated, containing each about 170 
grains of water, I filled them, one immediately 
after the other, from a bottle generating oxy- 
muriatic acid copiously ; into one of these, 
200 measures of olefiant gas were slowly trans- 
ferred ; after standing some time, the residuary 
gas was transferred and noted ; then the other 
tube with acid gas was taken, the gas passed 

5 or 6 times through water, till no further di- 
minution was observed, and the residuary gas 
was noted and allowed for impurity in the first 
tube. By this procedure no acid gas was lost, 
and an excess of olefiant gas being used, the 
purity of this last did not enter into the calcu- 
lation. In one trial, 165 measures of oxymu- 
riatic acid gas condensed 168 of olefiant gas ; 
in another, 165 took 167. From these, I 
conclude that oxymuriatic acid requires a very 
little more than its bulk of olefiant gas to be 
saturated : perhaps 100 of the former may take 


102 measures of the latter ; but if we reckon 
equal volumes, the error cannot in general be 

defiant gas burns with a dense, white 
flame. It explodes with uncommon violence 
when mixed with oxygen and electrified ; the 
products resulting are various, according to the 
circumstances. When completely saturated 
with ox-vgen, the results are, according to 

c*rb. acid. 

Berthollet, 100 measures take 280 oxygen, produce 180 
Dr. Henry, 100 — — 2S4. — — 179 

The rest of the produce is water. These 
results, agreeing so well with each other, arc 
the more plausible ; but I can add that my 
own experience corroborates thepti, particu- 
larly in regard to oxygen : My results have 
always given less than 300, but more than 270; 
the acid, I apprehend, should be about 185 
or 190: unless a great excess of oxygen be 
used, the charcoal is partly thrown down, and it 
makes the gas turbid after the explos'on ; the 
result in this case affords less carbonic acid 
than is due. 

When defiant gas a!one is subjected to con- 
tinued electricity, either over mercury or wa- 
ter, the result is hydrogen gas, and a quantity 
of charcoal is deposited. A very careful ex- 
periment of this kind was made by Dr. Henry 


and myself, in which 42 measures of pure 
defiant gas were electrified till they became 
82 ; these were exploded with oxygen, and 
found to consist of 78 hydrogen, and 2 de- 
fiant gas. Mere 40 olefiant became 78 hy- 
drogen, or very near double. The charcoal 
was thrown down. According to this, 100 
measures of olefiant gas will contain 195 of 
hydrogen ; which require 98 oxygen for their 
combustion ; now as the charcoal must take 
the rest, or nearly 196 measures, it follows that 
in the combustion of olefiant gas, 2 parts of 
the oxygen are spent upon the charcoal, and 1 
part upon the hydrogen, flence we obtain 
this conclusion, that an atom of olefiant gas 
consists of 1 of charcoal and 1 of hydrogen 
united. No oxygen can be present in olefiant 
gas; because during the elec'rification it would 
be detected, either in the form of water or 
carbonic oxide. 

It will be proper now to see how far the 
weights of the gases entering into combination, 
agree with the previous determinations. An 
atom of charcoal weighs 6.4 (see page 382), 
and 1 of hydrogen weighs 1, together making 
an atom of olefiant gas, 6.4. I'his atom will 
require 3 of oxygen for its combustion ; 
namely, 2 for the charcoal, to form carbonic 
acid, and 1 for the hydrogen, to form water ; 


these 3 weigh 21 ; whence 6.4 parts of olefiant 
gas by weight, should take 21 of oxygen. 
Now supposing, according to Dr. Henry's re- 
sult, that 100 measures of olefiant gas require 
284 for their combustion j and further, that 
the specific gravity of oxygenous gas is 1.10 
(agreeably to Alien and Pepys, as also Biot 
and Arago), we shall have 284 X i.i =312.4, 
the weight of the oxygen j hence, if 21 : 6.4 : : 
312.4:95, the weight of 100 measures of 
olefiant gas, corresponding to a specific gravity 
of .95. Hence, then, it appears that the 
weight of the gases combined, perfectly corro- 
borates the above conclusions respecting the 
constitution of olefiant gas. 

There are some remarkable circumstances 
attending the combustion of olefiant gas in 
^^olta's eudiometer, which deserve notice as 
part of the history of the gas, but particularly 
as they put the constitution of the gas beyopd 
all doubt. If 100 measures of oxygen be put 
to 100 of olefiant gas, and electrified, an ex- 
plosion ensues, not very violent ; but instead 
of a diminution, as usual, there is a great 
increase of gas ; instead of 200 measures, there 
will be found about 360 ; some traces of car- 
bonic acid are commonly observed, which dis- 
appear on passing two or three times through 
lime water i there will then remain, perhaps. 


550 measures of permanent gas, which is all 
combustible, yielding by an additional dose of 
oxygen, carbonic acid and water, the same as 
if entirely burnt in the first instance. What, 
therefore, is this new gas in the intermediate 
state ? The answer is clear. It is carbonic 
oxide and hydrogen mixed together, an equal 
number of atoms of each. One third of the 
oxygen requisite for the complete combustion, 
suffices to convert the carbone into carbonic 
oxide, and the hydrogen at the instant is li- 
berated ; hence the other two thirds are em- 
ployed, the one to convert the carbonic oxide 
into acid, the other to convert the hydrogen 
into water. In fact, the 350 measures consist 
of nearly 170 of each gas, which together re- 
quire nearly 170 of oxygen for their com- 

* M. Berthollet contends, that all the combustible gases 
into whk'h carbone and hydrogen enter, contain also oxy- 
gen : he calls them oxj/carburelted hydrogen. Mr. Murray 
also enters into his views in this respect. — As far as relates 
to olefiant gas, it will be time enough for animadversion 
on this opinion, when the accuracy of the above facts and 
observations are questiofled. But there is one circumstance 
which M. Berthollet has not explained in regard to tliis 
gas, and it turns upon a point which he and I acknowledge, 
but which is not perhivps generally received ; namely, that 
when tico gases unite to form a third, this las^ 2v specifically 
heavier ikon the lighter of the two. Now, in the above 


The diameter of an atom of olefiant gas is 
.81 to hydrogen J. And 100 measures of it 
contain as many atoms as 188 of hydrogen, or 
as 94 of oxygen, or (probably) as 200 of oxy- 
muridtic acid ; whence the union of this last 
with olefiant gas, must be 2 atoms of the gas 
with 1 of the acid. 

2. Carhurettcd Hydrogen. 

The gas which I denominate carburetted 
hydrogen, was known in a state of mixture, 
to Dr. Priestley ; he called all such mixtures 
by the name of lieaiij injiammabk air. La- 
voisier, Higgins, Austin, Cruickshanks, Ber- 
thollet, Henry and others, have since culti- 
vated this department of science. — Cruick- 
shanks contributed much to unveil th.^ subject, 
by pointing out carbonic oxide as an inflam- 
mable gas, sui generis, but often found mixed 
with other gases. No correct notion of the 
constitution of the gas about to be described, 
seems to have been formed till the atomic 

instance, \\v find olefiant gas and oxygenous gas, uniting 
to term a third (according to fiis opinion), vvljich. is lighter 
by oue half nearly than the lighter of the two. How is 
this new oxycarburetted hydrogen to be reconciled with 
the above principle ? 


ftieory was introduced and applied in the in- 
vestigation. It was in the summer of ISOI-, 
that I collected at various times, and in various 
places, the inflammable gas obtained from 
ponds; this gas I found always contained some 
traces of carbonic acid and a portion of azote; 
but that when cleared of these, it was of a 
uniform constitution. After due examination, 
I was convinced that just one half of the oxy- 
gen expended in its combustion, in Volta's 
eudiometer, was applied to the hydrogen, and 
the other half to the charcoal. This leading 
fact afforded a clue to its constitution. 

Carburetted hydrogen gas may be obtained 
in a pure state, with the above exceptions, 
from certain ponds in warm weather. Clayey 
ponds, in the vicinity of a town, where soot 
and other carbonaceous matter is deposited, 
abound with this gas. The bottom of the 
pond being stirred with a stick, large bubbles 
ascend, which may be caught by filling a 
tumbler with water, and inverting it over the 
ascending bubbles. This gas is obtained nearly 
pure also by distilling pitcoal with a moderate 
red heat. It is now largely used as a substitute 
for lamps and candles, under the name of coal 
gas. According to Dr. Henry's analysis, coal 
gas does not usually contain more than 4 or 5 
per cent, of carbonic acid, sulphuretted hydro- 


gen, and defiant gas. The rest is principally 
carburetted hydrogen, but mixed with some 
atoms of carbonic oxide and hydrogen. The 
last portion of gas driven off from pit-coal, 
seems to be entirely carbonic oxide and hydro- 
gen. The distillation of wood and of moist 
charcoal, and many other vegetable substances, 
produces carburetted hydrogen, but highly 
charged with carbonic acid, carbonic oxide 
and hydrogen ; the two last gases always appear 
exclusively at the end of the process. 

The properties of carburetted hydrogen are,. 
1. It is unfit for respiration, and for the sup- 
port of combustion. 2. Its specific gravity 
when pure, from my experience is very near 
.6. Dr. Henry finds the coal gas to vary from 
.6 to .78 ; but then the heaviest contain 15 
per cent, of the heavy gases, carbonic acid, 
sulphuretted hydrogen, and olefiant gas. — 
Water absorbs ^V^^ of its bulk of this gas.— If 
100 measures of carburetted hydrogen be 
mixed with 100 measures of oxygen (the least 
that can be used with effect), and a spark, 
passed through the mixture, there is an ex- 
plosion, without any material change of vo- 
lume : after passing a few times through lime 
water, it is reduced a little, manifesting signs 
of carbonic acid. This residue is found to 
possess all the characters of a mixture of equal 


volames of carbonic oxide and hydrogen. 
Upon adding 100 measures of oxygen to this 
residue and passing a spark, nearly 100 mea- 
sures of carbonic acid are produced, and the 
rest of the produce is water. If 100 measures 
of carburetted hydrogen be put to upwards of 
200 of oxygen, and. lired over mercury, the 
result will be a diminution of near 200 mea- 
sures, and the residuary 100 measures will be 
found to be carbonic acid. 

Though carburetted hydrogen is naturally 
produced in many coal mines, and occasionally 
mixing with common air, exhibits some dread- 
ful explosions in the large way ; yet when 
mixed with common air, in Volta's eudio- 
meter, it does not explode by a spark, unless 
the gas be to the air, as 1 to 10 nearly, and 
then feebly. 

When a portion of carburetted hydrogen gas 
is electrified for some time, it increases in 
volume, in the end almost exactly doubling 
itself J at the same time a quantity of charcoal 
is deposited. The whole of the gas is then 
found to be pure hydrogen. 

All these facts being compared, there can- 
not remain the least doubt as to the constitution 
of carburetted hydrogen. It is a compound 
of one atom of charcoal and two of hydrogen ; 
the compound atom occupies the same space 


(nearly) as an atom of hydrogen ; and 4 atoms 
of oxygen are necessary to its complete com- 
bustion ; namely, 2 for the charcoal to form 
carbonic acid, and 2 for the hydrogen to form 
water. This conclusion derives a very elegant 
confirmation, from the facts observed by ex- 
ploding the gas with one half of the oxygen 
requisite for complete combuslion. In this 
case, each atom of the gas requires onlv 2 
atoms of oxygen^ the one joins to one of hy- 
drogen and forms water ; the other joins to 
the carbone to form carbonic oxide, at th6 
same moment the remaining atom of hydrogen 
springs off. Thus there becomes 100 measures 
of carbonic oxide and 100 of hydrogen, or the 
same bulk, as the original mixture. 

As the weight of an atom of charcoal is 5.4, 
and 2 atoms of hydrogen arc 2, the compound 
atom weighs 7.4 ; but as there are the same 
number of atoms of hydrogen and of carbu- 
retted hydrogen in the same volume, 7.4 repre- 
sents the number of times that carburetted 
hydrogen is heavier than hydrogen. Now, the 
weight of common air is about 12 times as 
great as hydrogen ; therefore, the relative 
weights or specific gravities of the two gases, 
are as 7.4 to 12, or as .6 to 1, nearly, which 
agrees with experience j hence we derive this 
conclusion, that carburetted hydrogen consists 


entirely of hydrogen and carbone, the whole 
weight of the gas being accounted for in the 
carbonic acid and water formed by its com- 

I think it proper to observe, that, according^ 
to my most careful experiments, 100 measures 
of this gas require rather more than 200 mea- 

* According to M. Berthollet (IVJem. d'Arcueil, tome 2cl) 
ihe gas from chrircoal is a triple compound of carbone, 
oxygen, and bydiogen. Whatever our speculative che- 
mists may believe, no practical chemist in Britain adopts 
this idea. That it always contains more or less of oxygen 
no one disputes ; but then the oxygen is united solely to 
the carbone forming carbonic oxide. The rest of the mix- 
ture consists of carburetted hydrogen and hydrogen. I 
never find any difficulty in ascertaining the relative quan« 
Jlities of each* of the gases in such mixtures. For instance^ 
suppose we take the first of Berthollel's nine specimens. 

100 gas, sp. gr. .462 took 81 oxy. gave 56 carb. acid. 

20 carb. byd. sp. gr. .6 takes 42 gives 21 

34 r;irb. ox. .9t 16 32 

46hyd. ■ .08 23 

JOG raixt .476 takes 81 gives53 

Here it nppeais, that 20 measures of carb. hyd. -f- 34 
carb. oxide -f- 46 hydrogen, constitute a mixture of 100 
tripasures of the sp. grav. .476, which being burned, take 
81 oxygon, and give 53 carb. acid. Hence this mixture 
may be considered as agreeing with Bert hoi let's gas from 
charcoal above specified. 


sures of oxygen, and give rather more than 
100 carbonic acid ; but the difference is not 
more than 5 per cent, and may in general be 
neglected. — Hence, then, we may conclude 
that the diameter of an atom ot' carburetted 
hydrogen is nearly equal to that of hydrogen, 
but rather less. 



There are two compounds of hydrogen with 
sulphur ; the one, a well known elastic fluid 
denominated sulpJiuretted hydrogen, the other 
a vitjcid, oily compound, called supersulphii- 
retted hydrogen. The former of these consists 
of 1 atom of each element,* the the latter pro- 
bably of 1 atom of hydrogen united to 2 of 

1. Sulphuretted Hydrogen, 

The best way I have found to ob'ain sul- 
phuretted hydrogen in a pure state, is to heat 
a piece of iron to a white or welding heat in a 

* The figure for sulphuretted hy<lrogen, plate 4, part 1, 
is incorrect : it ought to be I atom of hyiliogen instead ol i, 
united to 1 of suipiiur. 


smith's forge, then suddenly drawing it from 
the fire, apply arollof sulphur ; the two being 
rubbed together, unite and run down in a 
liquid form, which soon fixes and becomes 
brittle. This compound or sulphuret of iron, 
is to be granulated and put into a gas bottle, 
to which dilute sulphuric acid is to be added, 
after which the gas comes over plentifully. 
When the sulphuret of iron is made in a cru- 
cible from iron filings and sulphur, it seldom 
answers well ; it often gives hydrogen mixed 
with the sulphuretted hydrogen. The reason 
seems to be, that several sulphurets of iron 
exist ; namely, the first, the second, the third, 
&c. and it is the second only, or that which is 
constituted of I atom of iron and 2 of sulphur, 
formed in the process above described, which 
is essential to the formation of sulphuretted hy- 
drogen. The others either give hydrogen or 
no gas at all. 

Sulphuretted hydrogen is unfit for respiration 
and for supporting combustion : it has a disa- 
greeable smell, resembling that of rotten eggs ; 
its specific gravity is 1.10 according to Kirwan, 
and 1.23 according to Thenard. Mr. Davy, 
I understand, makes it about 1.13. Some trials 
ofmineafew years since, gave a result near 
Thenard's ; but till a more correct one can be 
obtained, we may adopt the mean 1.16. Wa- 


ter absorbs just its bulk of this gas ; when'y 
therefore, it is mixed with hydrogen, th:s last 
will be left after washing in water, or wha^ 
is still better, in lime water. Sulphure'tcd 
hydrogen burns with a blue flame. When 
mixed with oxygen, in the ratio of 100 mea- 
sures to 50 of oxygen (which is the least ef- 
fective quantity), it explodes by an electric 
spark. ; water is produced, sulphur is depo- 
sited, and the gases disappear. If 150 or more 
measures of oxygen are used, then after the 
explosion over mercurv, about 87 measures of 
sulphurous acid are found in the tube, and 
150 of oxygen disappear, or enter into com- 
bination with both the elements of the gas. 

From the experiments of Austin, Henry, 
&c. it has been established, that sulphuretted 
hydrogen undergoes no change of volume by 
electrification, but deposits sulphur. I have 
repeated these experiments, and have not 
been able to ascertain whether there was in- 
crease or diminution. The residue of gas Is 
pure hydrogen. 

From these facts, the constitutian of sul- 
phuretted hydrogen is clearly pointed out. It 
is 1 atom of sulphur and 1 of hydrogen, united 
in the same volume as 1 of pure hydrogen. 
When burned, 2 atoms of oxygen unite to 1 
of sulphur to form sulphurous acid, and 1 of 


oxygen to 1 of hydrogen to form water. The 
weights of the (flements confirm this consti- 
tution. One atom of sulphur has been found 
to weigh 'S (see page 393), to which adding 
1 for hydrogen, we obtain the weight of an 
atom of sulphuretted hydrogen =14; this 
number Irkewise expresses the number of times 
that sulphuretted hydrogen should exceed hy- 
drogen in specific gravity. But common air 
exceeds hydrogen 12 times ; therefore, 12 : 
14 : : specific gravity of common air : sp. gra- 
vity of sulphuretted hydrogen = 1.16, agree- 
ably to the preceding determination. Hence 
this gas is wholly composed of sulphur and 
hydrogen, as above. 

Sulphuretted hydrogen unites, like the acids, 
to alkalies, earths, and metallic oxides, form- 
ing with them salts ot definite proportions, 
which are called hydrosulphyrrff; Some of 
thes<* are important chemical agents ; but they 
are apt to undergo changes by keeping, espe- 
cially in solution. 

2. Supersulplmrctted Hydrogen. 

This compound may be obtained as follows : 
Let half an ounce of flower of sulphur and as 
much hydrate of lime, be gently boiled toge- 
ther in a quart of rain water for one hour;. 


more water may be added as it evaporates. 
After cooling, a clear yellow li-quid is ob- 
tained, which is a solution of sulphuret of 
lime: it will vary in specific gravity from l.Ot 
to 1.02, according to circumstances. — To 6 
ounces of this liquid put half an ounce of mu- 
riatic acid, and stir the mixture. In a short 
time, the mixture exhibits a milky appearance,. 
and this becomes interspersed with brown oily 
dots, which gradu-ally subside into an adhesive 
mass of a semiliqaid form at the bottom. The 
liquid may then be poured off, and the brown 
mass washed with water, which is to be 
poured off. From 20 to 40 grains of this brown 
oily substance will be obtained ^ it is super- 
sulphuretted hydrogen. 

Scheele, Berthollet, and Proust, have made 
observations on this compound. When ex- 
posed to the ahr, or even in water, it exhales 
sulphuretted hydrogen, especially if warm. 
On account of its viscidity and adhesiveness, 
it is very dif^cult to subject it to experience. 
If a portion of it touch the skin, &c. it requires 
a knife to scrape it off. It may be poured 
from one vessel to another by means of water, 
which prevents its adhering to the vessel. 
"When a little of it is appplied to the tongue, a 
sensation of great heat, and a bitter taste arc 
felt ; the saliva becomes white like milk. 


When liquid alkali is poured upon supersul- 
phurettcd hydrogen, heat is produced, hydro- 
sulphuret is formed, and sulphur precipitated. 
— These fects have all been observed by mcj 
though few if any of thera are new. 

There is no doubt this substance Is formed 
of sulphur and hydrogen. I took 30 grains, 
and exposed them to a moderate h^at in a 
glass capsule, over a candle, till they ceased to 
exhale sulphuretted hydrogen. The residuum 
weighed 21 grains; it was soft like clay 4 
when ignited, it burned away with a blue 
flame, and left no sensible residuum. When 
it is considered, that supersulphuretted hy- 
drogen is from trie moment of its formation 
exhaling sulphuretted hydrogen, we cannot 
wonder that a portion of it should give less 
than half its weight of this gas. But scarcely 
any doubt can be raised that the sulphur of 
the gas is originally equal to that left behind ; 
or that supersulphuretted hydrogen is consti- 
tuted of 2 atoms of sulphur and 1 of hydrogen, 
and consequently weighs 27 times as much as 

Though it is not our present business to ex- 
plain the previous process by which the article 
under discussion is obtained ; yet, as it will be 
some time before it comes regularly in our 
way, it may perhaps be allowable. Hydrate 


of lime, is 1 atom of lime and 1 of water 
united ; when boiled with sulphur as above, 
it takes 3 atoms of sulphur. The compound 
is sidphurct of hijdrate of lime. When mu- 
riatic acid is mixed with it, the acid seizes the 
lime. The 3 atoms of sulphur divide the atom 
of water in such sort, that two of them take the 
hydrogen to form supersulphnretled hydrogen, 
and one takes the oxygen to form sitlphurous 
oxide. This last occasions the milkiness of 
the liquid ; by long digestion the milkiness 
vanishes -, the sulphurous oxide is changed into 
sulphuric acid and sulphur, which last falls 
down, and forms nearly one fourth of that 
which originally existed in the sulphuret. 



There is only one combination of hydrogerj 
with phosphorus yet known ; it is a gas deno- 
minated ])hnspJnirelted hydrogefi. This gas 
may be procured as follows : Let an ounce or 
two of hydrate of lime (dry slacked lime) be 
put into a gas bottle or retort, and then a few 
small pieces of phosphorus, amounting to 40 
or 50 grains. If the materials are sufficient tq 


fill the bottle, no precaution need be used ; 
but if not, the bottle or retort should be pre- 
viously filled with azotic gas, or some gas not 
containing oxygen, in order to prevent an ex- 
plosion. The heat of a lamp is then to be ap- 
plied, and a gas comes which may be received 
over water. This gas is phosphuretted hy- 
drogen ; but sometimes mixed with hydrogen. 
— Liquid caustic potash may be used instead 
of hydrate of lime, in order to prevent, the ge- 
neration of hydrogen. 

Phosphuretted hydrogen gas has the fol- 
lowing properties: 1. When bubbles of it 
come into the atmosphere, they instantly take 
fire ; an explosion is produced, and a ring of 
white smoke ascends, which is phosphoric 
acid : 2. It is unfit for respiration, and for 
supporting combustion : 3. Its specific gravity 
is .85, ct>mmon air being denoted by unity : 

4. Water absorbs -^V^h of its bulk of this gas: 

5. If the gas be electrified, the phosphorus is 
thrown down, and there finally remains the 
bulk of the gas of pure hydrogen. In fact, 
the phosphorus is easily thrown down, either 
by electricity, by heat, or by being exposed 
to a large surface of water. In this respect, 
phosphuretted hydrogen is nearly related to 
sulphuretted hydrogen. 

Though phosphuretted hydrogen explodes 


when sent Into the atmosphere in bubbles, yet 
if sent into a tube of three tenths of an inch 
diameter, it may be mixed with pure oxygen, 
without any explosion. In ail the experiments 
I have made, which are more than 20, I never 
had an instance of a spontaneous explosion. 
In this case, an electric spark produces a most 
vivid light, with an explosion not very vio- 
lent ; phosphoric or phosphorous acid and wa- 
ter are produced. 

My experiments on the combustion of this 
gas give the following results : When 100 
measures of pure phosphuretted hydrogen are 
mixed with 150 of oxygen, and exploded, the 
whole of both gases disappears ; water and 
phosphoric acid are formed i when 100 mea- 
sures of the gas are mixed with 100 oxygen, 
and fired, the whole of both gases still disap- 
pears ; in this case, water and phosphorous 
acid are formed ; when 100 measures are 
mixed with less than 100 of oxygen, phos- 
phorous acid and water are formed, but part of 
the combustible gas remains unburnt. 

As this gas is liable to be contaminated with 
hydrogen, sometimes largely, on account of 
the facility it poiisesses of depositing phos- 
phorus, it is expedient to ascertain the exact 
proportion of phosphuretted hydrogen to hy- 
drogen in any proposed mixture. This I find 


may easily be done. Whenever a sufHcicnt 
quantity of oxygen is afforded, the whole of 
the combustible gas is consumed : The exact 
volume of oxygen and its purity must be 
noted ; the quantity of oxygen in the residue 
must also be noted. Then the total dimi- 
nution after the explosion, being diminished 
by the oxygen consumed, leaves the combus- 
tible gas. Now, as phosphuretted hydrogen 
takes 14 times its bulk of oxygen, and hydro- 
gen takes t its bulk of oxygen ; we shall ob- 
tain the following equations, if P denote the 
volume of phosphuretted hydrogen, H that of 
hydrogen, O that of oxygen, and S= P 4- H, 
the whole of the combustible gas. 

P = O — iS 
H= i|S— O 

From these equations, the ratio of the two' 
gases in any mixture is deduced. The ana- 
lysis may be corroborated as follows : To any 
mixture containing a certain volume of phos- 
phuretted hydrogen, let the same volume ot 
oxygen be added ; after the explosion, the 
diminution will be just twice the volume of 
oxygen. In this case, the phosphuretted hy- 
drogen is preferred by the oxygen ; phos- 
phorous acid, and water are formed, and the 
hydrogen remains in the tube. If more oxy- 


gen is put than the phosphuretted hydrogen, 
then the dinilnution after firing is more than 
twice the oxygen. 

The investigation respecting the proportion 
of hydrogen mixed with phosphuretted hy- 
drogen, was instituted chiefly in consequence 
of a difference of opinion respecting the spe- 
cific gravity of the latter gas. I had found 
100 cubic inches to weigh about 26 grains ; 
Mr. Davy infonned me he had found 109 
inches to weigh only 10 grains : the difference 
is enormous. I requested Dr. Henry wouki 
assist me in repeating the experiment. We 
obtained a gas, such that 100 inches weighed 
ll- grains ; this result surprized me ; but upon 
burning the gas with oxygen, it was found 
only to take its bulk of that gas, and conse- 
quently to be half hydrogen and half phos- 
phuretted hydrogen, which satisfactorily ex- 
plained the dilHculty. Mr. Davy's gas, I 
conceive, must have beer» f phosphuretted hy- 
drogen and y hydrogen, at the time it was 
weighed ; however this may be, it is evident, 
from what is related above, that nothing certain 
can be inferred relative to the specific gravity 
of this gas, unless a portion of the gas be ana- 
lyzed previously to its being weighed ; a cir- 
cumstance of which I was not at first suffici- 
ently aware. 


I have recently procured some phosphuretted 
hydrogen gas from caustic potash and phos- 
phorus ; an accident prevented me obtaining 
a sufficient quantity to weigh ; but I got 5 or 
6 cubic inches, which of course were mixed 
with the azotic gas previously put into the 
retort. The pure combustible gas was of 
such character, that 100 measures required 
only 85 of oxygen for their combustion j it 
was consequently 35 phosphuretted hydrogen 
and 65 hydrogen per cent, and probably 
would have weighed aftei the rate of 10 of 
11 grains for 100 cubic inches. I expected 
much purer gas. 

As to the constitution of phosphuretted hy- 
drogen, it is clearly 1 atom of phosphorus 
united to 1 of hydrogen, occupying the same 
space as 1 of elastic hydrogen. In combustion, 
the atom of hydrogen requires one of oxygen, 
and the atom of phosphorus requires one or 
two of oxygen, according as we intend to 
produce phosphorous or phosphoric acid. 
Hence it is that 100 measures of phosphu- 
retted hydrogen require 50 oxygen to burn the 
hydrogen, 50 more of oxygen to form phos- 
phorous acid, and 50 more to form phosphoric 
acid. The weight of the gas corroborates this 
conclusion : it has been seen that the atom of 
phosphorus weighs nearly 9 (page 415) ; this 


would make the specific graviry of phospbu- 
retted hydrogen equal to 10 times that of hy- 
drogen, which it actually is, or nearly so, from 
the foregoing experiments. 

The next compounds to be considered in 
course, would be those of azote with carboTWf 
with sulphur, and with phospJiorus ; but such 
compounds either cannot be formed, or they 
arc yet unknown. 



1 . Carbone with Sulphur. 

In the 42d vol. of the An. de Chimie, page 
136, Clement and Desormes have announced 
a combination of carbone and sulphur, which 
they call carburettcd sulphur. They obtain it 
by sending the vapour of sulphur over red hot 
charcoal ; it is collected in water in the form 
of an oily liquid of the specific gravity 1.3. 
This liquid is volatile, like ether, expanding 
any gas into which it i$ admitted, and forming 


SL permanent elastic fluid over the mercury of 
a barometer. No gas is produced at the same 
time as the liquid. When too much sulphur is 
driven through, instead of a liquid, a solid 
compound is formed which crystallizes in the 
tube. They seem to have shewn that the 
compound does not contain sulphuretted hy- 
drogen. — In the 64th vol. of the Journal de 
Physique, A. B. Berthollet endeavours to prove 
that the liquid in question is a compound of 
hydrogen and sulphur, and contains no char- 
coal. The facts adduced are not sufficient to 
decide the question either way. I should be 
unwilling to admit, with Clement and De- 
sormes, that the two inelastic elements, char- 
coal and sulphur, would form an elastic or vo- 
latile compound ; yet, they have rendered it 
highly probable that charcoal makes a part of 
the compound, as it disappears during the 
process. I think it most probable, that Ber- 
thollet is correct in the idea that this liquid 
contains hydrogen. We know of no other 
volatile liquid that does not contain hydrogen. 
Perhaps it will be found a triple compound of 
hydrogen, sulphur, and charcoal. 


2. Carbone ivith Phosphorus. 

A combination of carbone and pnosphorus 
has been pointed out by Proust, in the 49th 
volume of the Journal de Physique, which he 
names phosphuret. of carbone. It is the reddish 
substance which remains when new made 
phosphorus is strained through leather in warm 
water. The proportion of the two elements 
has not been ascertained. 

3. Sulphur with Phosphorus. 

Melted phosphorus dissolves and combines 
with sulphur, and that in various proportions, 
which have not yet been accurately ascer- 
tained. The compounds may be denominated 
sulphurets of phosphorus. The method of 
forming these compounds, is to melt a given 
weight of phosphorus in a tube nearly filled 
with water, and then to add small pieces of 
sulphur, keeping the tube in hot water, taking 
care not to exceed 160% or 170% or 180% be- 
cause the new compound begins to decompose 
water rapidly at those high temperatures. 
Pelletier has given us some facts towards a 
theory of these various combinartions, in the 


4th vol. of the An. de Chimie. He found 
that a mixture of sulphur and phosphorus re- 
mained fluid at a much lower temperature 
than either of them individually ; and that 
different proportions gave different fusing or 
congealing points. One part of phosphorus, 
combined with 4th of sulphur, congealed at 
77°; one part with ^, at 59"; one part with 4, 
at 50° ; one part with 1, at 41° ; one part with 
2, at 54°4 ; but a certain portion was fluid, 
and the rest solid ; and one part with 3j at 
99°. 5. 

One would be apt to think, from these ex- 
periments, that sulphur and phosphorus might 
be combined in all proportions ; but the ob- 
servation on the 5th led me to suspect that it 
might have been applied to some others if the 
results had been carefully noted. — I mixed 18|- 
grains of phosphorus ,nnd 13 of sulphur in a 
graduated tube, put in water, and immersed 
the whole into water of 160°. The phos- 
phorus having been rendered fluid as usual, at 
100°, gradually reduced the sulphur, till the 
whole assumed a liquid form of the specific 
gravity 1.44. It remained uniformly fluid at 
45°, but was wholly congealed at 42°. Here 
were two atoms of phosphorus united to one of 
sulphur. I (hefi added 6t grains of sulphur, 
making the mixture 18t phosphorus, and 19t 


salphur i this'new mixture was reduced to uni- 
form fluidity at 170% and was of 1.47 specific 
gravity; reduced to 47°, one part was fluid 
and the other solid, the latter being at the 
bottom of the tube. This solid part was not 
completely reduced to fluidity in the tempe- 
rature 100°. This seems to indicate that two 
distinct combinations took place j the one, 
two atoms of phosphorus and one of suiohur, 
Jiquid at 47° ; the other, one atom of phos- 
phorus and one of sulphur, solid under 100°. 
I next added 64- grains more of sulphur, mak- 
ing in the whole 18{ phosphorus and 26 sul- 
phur, consequently in such proportion as to 
afford a union of one atom of each ; the union 
was completed in a temperature of 180° : the 
specific gravity was 1.50 Cooled down to 
80°, the whole was solid ; heated to 100°, the 
whole became a semi-liquid, uniform mass. 
Being afterwards heated to 140°, the whole 
became fiui-^ ; but upon cooling again, the 
greatest part congealed at 100°, but |d or ^^th 
'•emained liquid down to 47°. — From these 
experiments, it is most probable that one atom 
of each forms a combination which is solid at 
lOO" or below ; but that being heated, it is 
apt to run into the other mode of combination, 
or that constituted of two atoms of phosphorus 
and one of svilphur. The properties of these 

POTASH. 467 

two species of sulphuret of phosphorus I have 
not had an opportunity to investigate. The 
water in the tube is evidently decomposed ia 
part by the compound ; it becomes milky, 
probably through the oxide of sulphur, and 
both sulphuretted and phosphuretted hydrogen 
seem to be formed in small quantities at tem- 
peratures above 1 60°. 



The fate of the two fixed alkalies, potash 
and soda, has been rather remarkable. They 
had long been suspected to be compound ele- 
ments, but no satisfactory proof was given. 
At length Mr. Davy, by his great skill and 
address in the application of galvanism to pro- 
duce chemical ciianges, seemed to have estab- 
lished the compound nature of these elements, 
both by analysis and synthesis. They appeared 
to be metallic oxides y or peculiar metals united 
to oxygen. Consistent with this idea, some 
account of the metals, denominated potasium 
and sodium, has been given in this work. (See 
page 260). But from what follows, it ap- 
pears most probable, that these metals are 


co'npoaixds of potash and soda with hydrogen, 
and that the two fixed alkalies still remain 
among the iindecompounded bodies. 

1. Potash. 

Potash is obtained from the ashes of burned 
wood. Water dissolves the saline matter of 
the ashes, and may then be poured oflF and 
evaporated by artificial heat : the salt called 
potash remains in the vessel. If the salt so 
obtained be exposed to a red heat, it loses 
combustible niaiter, becomes white, and is in 
part purified : in commerce it is then called 
pearl-ash. This mass is still a mixture of va- 
rious salts, but is constituted chiefly of car- 
bonate of potash. In order to obtain the pot- 
ash separate, let a quantity of peari-asli (or 
what is still better, salt of tartar of the shops, 
which is this pearl-ash reduced almost to pure 
carbonate of potash) be mixed with its weight 
of water, and the mixture be stirred ; after 
the undissolved salt has subsided, pour oflP the 
clear solution into an iron pan, and mix with 
it a portion of hydrate of lime, half the weight 
of the liquid j then add a quantity of water 
equal to the weight of the ingredient^, and 
boil the mixture for several hours, occasionally 
adding more water to supply the waste. When 



tVje liquid is found not to effervesce with acids, 
the ebullition may be discontinued. After the 
lime has subsided, the clear liquid is to be de- 
canted, and then boiled down in a clean iron 
pan till it assumes a viscid form, and acquires 
almost a red heat. It may then be poured 
into molds, &c. and it immediately congeals. 
The substance so obtained is potash nearly 
pure ; but it still contains a considerable por- 
tion of water, some foreign salts, oxide of 
iron, and frequently some unexpelled carbonic 
acid. The water may z\mount to 20 or 25 per 
cent, upon the whole weight, and the other 
substances to 5 or 10 per cent. In this pro- 
cess, the carbonic acid of the potash is trans- 
ferred to the lime. 

If potash of still greater purity be required, 
the method practised by Berthollet may be pur- 
sued. The solid potash obtained as above 
must be dissolved in alcohol j the foreign salts 
will fall to the bottom insoluble ; the liquid 
solution may then be decanted into a silver 
bason, the alcohol be evaporated, and the fluid 
potash exposed to a red heat. It may be 
poured out upon a clean polished surface, 
where it instantly congeals into solid plates of 
potash, which are to be broken and put into 
well stoppered bottles, to prevent the access of 
air and moisture. This potash is a solid, 


brittle, white mass, consisting of about Si 
parts potash and 16 water, in 100 parts, and 
is the purest that has ever yet been obtained. 

Potash may be exhibited in a more regular 
crystalline form by admitting more water to 
it. If the solution be reduced to the specific 
gravity of 1.6> or 1.5, upon cooling, crystals 
will be formed, containing about 53 per cent, 
of water, or more, if the air is cold. These 
crystals are called hydrate of potash. Hence 
solid hydrate of potash may be formed, con- 
taining from 84 per cent, of potash to 47, or 

Potash has a very acrid taste y it is exceed- 
ingly corrosive if applied to the skin, so as to 
obtain the name of caustic. The specific gra- 
vity of the common sticks of potash used by 
surgeons, I find to be 2. 1 j but these are a 
mixture or potash and carbonate of potash, 
with 20 or 30 per cent, of water. If pot-ash 
were obtained pure, I apprehend its specific 
gravity would be about 2.4. 

When crystals of potash (that is. the hy- 
drate) are exposed to heat, they become liquid, 
the water is gradually dissipated with a hissing 
noise, till at length the fluid acquires a red 
heat. It then remains tranquil for some time ; 
but if the heat be increased, white fumes be- 
gin to arise copiously. The alkali and water 

POTASH. 471 

both evaporate in this case ; therefore, the pro- 
cess cannot be used to expel the last portion of 
water from the alkali. If the hydrate be taken 
in the red hot and tranquil state, it contains 
84 per cent, potash and 16 water. This is 
ascertained by saturating a given weight of it 
wiih sulphuric acid, when sulphate of potash 
is formed free from water, and 100 parts of 
the hydrate give only 84 parts to the new 

Water has a strong affinity for potash. If a 
portion of the 84 per cent, hydrate be put into 
as much water, great heat is immediately pro- 
duced, equal to that of boiling water. But it 
is observable that the crystallized hydrate con- 
tainino' much water, when mixed with snow, 
produces excessive cold. When potash is ex- 
posed to the air, it attracts moisture and car- 
bonic acid, becoming a liquid carbonate. Pot- 
ash dissolved in water, and kept in a stoppered 
bottle, retains its causticity : it is called al- 
kaline ley, and may be had of various strengths 
and specific gravities. 

Potash, and the other alkalies, change ve- 
getable colours, particularly blues, into green. 
— Potash is of great utility in the arts and ma- 
nufactures, particularly in bleaching, dying, 
printing, soap and glass manufactures. It 
unites with most acids to form salts. It does 


not unite with any of the simple substances, 
as far as is yet known, except hydrogen, and 
that in a circuitous way, as will presently be 
noticed. The hydrate of potash unites with 
sulphur i but the compound, consisting of 
three or more principles, cannot yet be dis- 

The theory of the nature and origin of pot- 
ash still remains in great obscurity. The great 
question, whether it is a constituent principle 
of vegetables, or formed during their combus- 
tion, is not yet satisfactorily answered. One 
circumstance is favourable to the investigation 
of the nature of potash, the weight of its ulti- 
mate particle is easily ascertained ; it forms 
very definite compounds with most of the 
acids, from which it appears to be 42 times 
the weight of hydrogen. The following pro- 
portions of the most common salts with base 
of potash, are deduced from my experience ; 
they are such that good authorities may be 
found both for greater and less proportions of 
the different elements. 

per cent. 

Carbonate of potash, 31.1, acid -j- ^S.Q base, as 19 : 42 

Sulphate 44.7 1- 55.^ 3* ; 42 

JNitrato 47.5 1- 52.5 'iS : 42 

Muriate 34. t [- 65.6 22 : 42 

POTASH. 473 

The above salts are capable of sustaining a 
red heat, and may therefore be supposed to 
be free from water ; at all events, the potash 
must contain the same quantity of water in 
combination with the respective acids, as ap- 
pears from the uniformity of its weight. The 
above numbers, 19, 34, 38 and 22 represent., 
as the reader will recollect, the weights of the 
atoms of the respective acids, except the nitric, 
which is double. As water has so strong an 
afTinity for potash, and as the weight of the 
elementary particle of potash above deduced 
is more than five times that of water, it may 
still be supposed that water enters into the 
constitution of potash, or that it is compounded 
of some of the lighter earths with azote, oxy- 
gen, &c. From present appearances, how- 
ever, the notion that potash is a simple sub- 
stance seems more probable than ever. 

From the above observations, it appears that 
potash ought still to be considered as a simple 
substance, and would require to be placed 
among such substances, but that it cannot be 
obtained alone. In that state which ap- 
proaches nearest to purity it is a hydrate, con- 
taining at least I atom of water united to 1 of 
potash, amounting to 16 per cent, of water. 
This hydrate is therefore a ternari) compound, 
or one of three elements, and ought to be post- 


poned till the next chapter : but, in the pre- 
sent state of chemical science, utility must be 
allowed in some instances to supersede me- 
thodical arrangements. The fixed alkalies are 
most useful chemical agents, and the sooner 
we become acquainted with them the better ; 
more especially, as some of the first chemists 
of the present age have been led into consi- 
derable mistakes, by presuming too much upon 
their knowledge of the nature and properties 
of these familiar articles. 

In the Memoires dc V Instilnt dc France^ 
1806, Berthollet published researches on the 
Jaws of afiinity, from which some extracts are 
given in the Journal de Physique for March 
1807.; — By these, it appears that he found sul- 
phate of barytes to consist of 26 acid and 74 
base, and sulphate of potash of 33 acid and 67 
base. The former of these results was corro- 
borated by the previous experience of The- 
nard ; but both are so remote from the uniform 
results of other chemists, that they could never 
be generally adopted. At length Berthollet 
discovered the error, and has announced it in 
the 2d vol. of the Memoires d'Arcueil. It 
consisted in mistaking the hydrates of barytes 
and potash for pure barytes and potash. It 
seems to have been generally adopted, but 
certainly prematurely, that barytes and potash, 


in a state of fusion, were pure, or free from 
water. But upon due investigaiion, he found 
that fused potash contains 14 per eent. of wa- 
ter I my experience as well as theory, leads 
me to adopt 16 percent, of water, which ac- 
cords with the position of 1 atom of each of 
the elements uniting to form the hydrate ; 
namely, 42 by weight of potash with 8 of 
water. This discovery reconciles the jarring 
results on the proportions of the above neutral 
salts, and throws light upon some other inter- 
esting subjects of chemical analysis. 

2. Hijdvate of Potash, 

Upon turning my attention to this subject, 
I soon perceived the want of a table exhibit- 
ing the relative quantities of potash and water 
in all the combinations of these two element*. 
In a state of solution, the specific gravity may 
be taken as a guide ; but this is not quite so 
convenient when the compound is in a solid 
form. I found nothing of the kind in any 
publication, and therefore undertook a course 
of experiments to determine the relative quan- 
tities of potash, &c. in the various solutions. 
The results are contained in the following 
table, which I would have to be considered 



only as an approximation to truth ; but it wili 
certainly have its use till a more complete and 
accurate one be obtained. Dr. Henry was so 
obliging as to facilitate my progress, by pre- 
senting me with portions of the fixed alkalies, 
prepared after Berthollet's method. 

Table of the ijuantity of real potash in watery solution* 
of different specific gravities, &c. 




pci cent. 

per rent. 




Potash Water 

by wciglit.. 

by measure. 










J+ 1 





red heat 

1+ 2 






1+ 3 






1+ t 



1.7 8 



1+ 5 






1-1- 6 






1-f ' 





27 6« 

1-h 8 






1+ !> 



1 .44 


































1 . 15 










Remarks on the Table. 

The first column contains the number of 
atoms of potash and water in the several com- 


binatlons to 10 atoms of water : the weight of 
an atom of potash is taken to be 42, and 1 of 
water 8. From these data the second column 
is calculated. There did not appear any strik- 
ing characteristic of distinction between the 
first, second, third, &c. hydrates, (if they may 
be so called) except that the first bears a red 
heat in the liquid form, with tranquillity and 
without loss of weight. Before this, the wa- 
ter is gradually dissipated with a hissing noise 
and fumes. I remarked, however, that when 
a solution of potash is boiled down till the 
thermometer indicates upwards dF 300°, the 
evaporation of the water, and the rise of the 
thermometer, are desultory ; that is, the ope- 
rations appear somewhat stationary for a time, 
and then advance quickly ; how far this may 
arise from the nature of the compound, or 
from the imperfect conducting power of the 
liquid in those high temperatures, I could not 
determine without more frequent repetitions 
of the experiment. 

The third column Is, as usual, obtained by 
multiplying the second column by the specific 
gravity ; it is often more convenient in prao- 
tice to estimate quantity by measure than by 

The fourth column denotes the specific gra- 
vity ; below 1.60 the hydrate is completely 


fluid, or may be made so by a moderate heat ; 
but above that temperature, I found some dif- 
ficulty in ascertaining the specific gravity, and 
was obliged sometin^es to infer it from the 
tenor of the table. The common sticks of 
potash of the druggists are of the sp. gr. 2.1, 
which I found by plunging them into a gra- 
duated tube filled with mercury, and marking 
the quantity that overflowed. These sticks 
are a mixture of hydrate and carbonate. Real 
potash must, I conceive, be heavier than they 
are. The relation of the second and fourth 
columns was ascertained by taking a given 
weight of the alkaline solution, saturating it 
with test sulphuric acid (1.134), and allowing 
21 grains of alkali for every 100 measures of 
acid (containing 17 real) which the alkali re- 

The 5th column denotes the temperatures at 
which the different hydrates congeal or crys- 
tallize. This part of the subject deserves much 
more accurate enquiry than I have been able 
to bestow upon it. No doubt the diflPerent 
hydrates might be distinguished this way. 
Proust talks of a crystallized hydrate of potash, 
containing '30 per cent, of water ; and Lowitz 
of one containing 43 per cent, of water. They 
calculate, I presume, upon the supposition of 
fused potash being free from water j if so. 


Proust*s hydrate is the fourth of our table, and 
Lowitz's the sixth. I would not have much 
trust to be put in the temperatures I have 
marked in this column. 

The sixth column indicates the temperatures 
at which the different specific gravities boil. 
This is easily ascertained, except tor the high 
■degrees, in which an analysis of the hydrate 
was required upon every experiment. I believe 
the results will be found tolerably accurate. 
As the range of temperature is large, this may 
be found a very convenient method of ascer- 
taining the strength of alkaline solutions, when 
the specific gravities are unknown. 

3. Carbonate of Potash. 

Though it be premature to enter into the 
nature of carbonate of potash, a triple com- 
pound, yet its utility as a test is such as to 
require it to be noticed in the present section. 
Indeed it may generally be a substitute for the 
hydrate of potash, and it can much more rea- 
dily be procured in a state of comparative 
purity. The carbonate 1 mean is that which 
consists of one atom of acid united to one of 
potash, which by some writers is called a suh- 
carboiiate. It is, of course, constituted of J 9 


parts of acid by weight united to 42 of potash. 
This salt is to be had in tolerable purity of the 
druggists, under the name of salt of tartar ; 
but when it is to be used in solution for pure 
carbonate, a large quantity of the salt, and a 
small quantity of water, are to be mixed and 
agitated ; then let the undissolved salt subside, 
and pour off the clear solution, which may be 
diluted with water, 8ic. 

This salt is well known to be, like the dry 
hydrate of potash, very deliquescent. I took 
43 grains of carbonate of potash that had just 
before been made red hot, put them into a 
glass capsule exposed to the air; in one day 
the weight became 60 grains ; in three days, 
61 grains; in seven days, 75 grains; in II 
days, 89 grains ; in 21 days, 89+ grains ; in 
25 days, 90 grains. The specific gravity was 
1.54 nearly. All the water is, however, driven 
oft by a moderate heat ; namely, that of 280°. 
It supports a high red heat before fusion, and 
when fused loses no weigh!, remaining with- 
out sublimation, and undecompounded. I 
ascertained that it was a perfect carbonate, by 
dissolving 61 grains of pure dry salt in lime 
water, when 42 grains of carbonate of lime 
were thrown down, corresponding to 19 grains 
of carbonic acid. 



Table of the quantity of real carbonate of potash in watery 
solutions of different specific gravities, 


Curb. Potl'h 

Ctrb. Potath 

per cent. 

per cent. 




by weight. 

by niea»ure. 



afi'ot. Water 






1+ I 





1+ 2 





1+ 3 





1+ 4 





1+ 5 





1+ 6 










1-f- 8 




235 » 

1+ 9 





I + IO 

















33. t> 
















20 5 




















This table is similar in structure to the pre- 
ceding. The first column contains the number 
of atoms of water joined to one of carbonate of 
potash, which last weighs 61. The second 
contains the weight of carbonate of potash per 
cent, in the compound, and the third the 
grains of carbonate in 100 water grain mea- 
sures of the compound, found by multiplying 


the nuawbers in the second and fourth columns 
together. The fourth contains the specific 
gravities ; the relations of these to the quan- 
tities in the second column were found, by 
taking a given weight of the solution, arid sa- 
turating it with a certain number of measures 
of test sulphuric acid (1.134), allowing 21 real 
potash, or 30^ carbonate, for every 100 mea- 
sures of acid required ; because such acid con- 
tains 17 per cent, by measure of real sulphuric 
acid, and that requires 21 of potash. 

The strongest solution of this salt that can be 
obtained is of the specific gravity 1.54. This 
consists of 1 atom of carbonate and 8 of water ; 
but by putting dry carbonate into that solution, 
various mixtures may be formed up to the spe- 
cific gravity 1.80 ; above that the specific gra- 
vity is scarcely to be obtained but by inference. 
I could not obtain a solid stick of fused car- 
bonate but what was spongy, I suppose from 
incipient decomposition. It may be observed, 
that the specific gravity 1.25, which contains 
30 per cent, of carbonate, is that which I 
prefer as a test for acids ; because the solution 
contains 21 per cent, pure potash, and 100 
measures of it consequently require 100 mea- 
sures of the test acids. 

I found a specimen of the pearl-ash of com- 
merce to contain 54 parts carbonate of potash. 


22 parts of other salts, and 24 parts of water 
in the hundred. 

The fifth column denotes the temperature 
at which the saline solutions boil. This will 
be found generally a ^ood approximation to 
truth, I observed the thermometer did not 
rise above 2W as long as any visible moisture 
remained; as soon as that vanished, the salt 
assumed the character of a hard and perfectly 
dry substance. 

In the course of these experiments, I took 
a quantity of carbonate of potash, and heated 
it red hot > then weighed it ; after which I 
put to it as much water as afforded 1 atom to 
1 ; namely, 8 parts water to 61 salt. The 
salt was then pulverized in a mortar ; it was 
put out upon white paper, and appeared a 
white, dry salt ; but upon pouring it back 
into the mortar, some particles of the salt ad- 
hered to the paper. The same quantity of 
water was again put to it. Upon mixing 
them with a knife, the whole mass assumed a 
pasty consistence, and adhered to the knife in 
the shape of a ball ; after being well rubbed 
in the mortar, it again assumed a white, dry 
appearance. Upon paper, it seemed like salt 
of tartar some time exposed to the air. Several 
particles stuck to the paper, but were easily 
removed by a knife. The addition of another 


atom of water redueed the compound to the 
consistence of bird-lime ; but after standing 
it cut like half dried clay. The next atom of 
water reduced it to the consistence of book- 
binders paste. The fifth atom of water re- 
duced it to a thick fluid, consisting of dis- 
solved and undissolved salt. This^ by the suc- 
cessive application of like portions of water, 
became a perfect fluid with 8 atoms of water 
to 1 of carbonate of potash. Its specific gra- 
vity was 1.5 ; but there was some undissolved 
sulphate of potash subsided, the salt of tartar 
not having been previously purified. 

4. Potasium, or Hydriiret of Potash. 

Since writing the articles on Potasium and 
Sodium (page 260 and seq.), and the subse- 
quent articles on fluoric and muriatic acid 
(page 277 and seq.), a good deal more light 
has been thrown on these subjects. Two pa- 
pers on the subjects have been published by 
Mr. Davy ; a series of essays by Gay Lussac 
and Thenard, are contained in the 2d vol. of 
the Memoires d'Arcueil ; the same volume 
also contains a paper by Berthollet, announc- 
ing an important discovery relating to the fixed 
alkalies i namely, that in a state of fusion by 


heat, they contain a definite proportion of 
water in chemical combination. Upon re- 
considering the former facts, and comparing 
them with the more recent ones, I am obliged 
to adopt new views respecting the nature of 
these new metals. Mr. Davy still adheres to 
his original views, and which indeed were the 
only rational ones that could be formed (sup- 
posing the fused alkalies to contain no water), 
namely, that potash is ihe oxide of potasium ; 
Gay Lussac and Thenard, on the contrary, 
consider potash as undecompounded, and po- 
tasium a compound of hydrogen and potash, 
analogous to the other known compounds of 
hydrogen and elementary principles. This 
last is the only one, I think, that can be ad- 
mitted either from synthetic or analytic expe- 
riments, so as to be reconcileable with the 
facts ; but I do not coincide with all the con- 
clusions which the French chemists have de- 
duced. Mr. Davy has furnished us with the 
most definite and precise facts ; and though I 
was led to controvert some of them (see page 
289 and seq.), it was principally through my 
having adopted his views of the nature of po- 
tasium : I am now persuaded those results were 
more accurate than I imagined. 

Mr. Davy first attempted to decompose the 
fixed alkalies, by applying Voltaic electricity 


to saturated watery solutions ; in this case, 
oxygen and hydrogen gas were obtained, evi- 
dently proceeding, as he concluded, from the 
decomposition of the water. But when any 
potash that had previously been fused, was 
substituted for the watery solution, no hydro- 
gen gas was given out at the negative pole, 
but potasium was formed, and pure oxygen 
was given out at the positive pole. The re- 
sidual potash was unaltered. The conclusion 
he drew was, that the potash was decomposed 
into potasium and oxygen. But it now ap- 
pears, that fused potash is composed of 1 atom 
of water and 1 of potash. "1 he electricity 
operates upon this last atom of water to se- 
parate its elements ; it succeeds in detaching 
the atom of oxygen, but that of hydrogen 
draws the atom of potash along with it, form- 
ing an atom of potasium. The atom of hy- 
drate weighing 50 (= 42 potash + 8 water) is 
decomposed into one of potasium, weighing 
43, and one of oxygen weighing 7. Hence 
the atom of potasium is composed of 1 pot- 
ash -f 1 hydrogen, weighing 4 3 ; and not of 
1 potash — 1, oxygen, weighing 35, as stated 
at page 262. 

The method of obtaining potasium, disco- 
vered by the French chemists, is to find the 
first hydrate of potash in a state of vapour over 


red hot iron turnings, in an iron tube intensely 
heated ; hydrogen gas is given out, potasium 
is formed and condensed in a cool part of the 
tube, and part of the potash is found united 
to the iron. In this mode of producing pota- 
sium, its constitution is not so obvious as in 
the former. The two methods, however, to- 
gether, shew that fused potash contains both 
oxygen and hydrogen, which is now abun- 
dantly confirmed by experiments of a different 
kinJ. It seems probable that in the latter 
method the hydrate of potash is partly decom- 
posed into potash and water, and partly into 
potasium and oxygen ; in both cases the iron 
acquires the oxygen. 

The specific gravity of potasium is .6, or 
.796, according to Davy ; but .874 according 
to Gay Lussac and Thenard. The levity of it, 
combined with its volatility at a low red heat, 
agrees with the notion of its being potash and 
Hydrogen, or pofassetted hydrogeiu resembling 
the other known compounds of sulphur, phos- 
phorus, charcoal, arsenic, &c. combined with 

When burned in oxygen gas, potasium pro- 
duces potash as dry as possible to be procured, 
according to Mr. Davy ; that is, the first hy- 
drate. When potasium is thrown into water 
it burns rapidly, decomposing the water, and 


giving off hydrogen. Calculating the oxygen 
from the quantity of hydrogen, Mr. Davy finds 
100 (hydrate of) potash contain from 13 to 17 
oxygen : Gay Lussac seems to make it 14-. 
For, 2.284 grammes of potasium gave 649 
cubic centimetres of hydrogen ; reduced, 35,5 
grains gave 34.5 cubic inches English measure, 
which correspond to 17.25 inches of oxygen 
= 5.9 grains. Hence 35.3 + 5.9 = 41.2 
grains of hydrate ; and 41.2 : 5.9 :: 100 : 14. 
But this is exactly the quantity that theory 
would assign ; for, 43 potasium + 7 oxygen 
= 50 hydrate, which gives just 14 oxygen in 
the hundred. 

Potasium burns spontaneously in oxymuriatic 
acid gas ; muriate of potash is formed, and 
probably water. It decomposes sulphuretted, 
phosphuretted, and arseniuretted hydrogen gas, 
according to Gay Lussac and Thenard, and 
unites to the sulphur, &c. with some of the 
hydrogen. Mr. Davy finds tellurium to unite 
with the hydrate of potash by Voltaic electri- 
city without decomposing it. Potasium burns 
in nitrous gas and nitrous oxide, forming dry 
hydrate of potash, and evolving azote. It 
burns in sulphurous and carbonic acid, and in 
carbonic oxide ; hydrate of potash which unites 
to the sulphur is formed, or hydrate of potash 
and charcoal. 


The combustion of potaslum in muriatic acid 
gas is particularly worthy of notice. Both Mr. 
Davy and the French chemists agree that when 
potasiura is burned in muriatic acid gas, mu- 
riate of potash is formed, and hydrogen evolved, 
which agrees in quantity with that evolved in 
the decomposition of water by the same quan- 
tity of metal. But, what is most astonishing, 
they both adopt the same explanation, when 
their different views of the constitution of po- 
tasium require them to be opposite. Mr. 
Davy had two ways in which he might ac- 
count fox the phenomenon ; the one was to 
suppose that a part of the acid was decom- 
posed, and furnished the oxygen to the metal 
fo form the oxide (potash), which joined to 
the remainder of the acid, and the hydrogen 
was an evolved elementary principle of that 
part of the acid decomposed ; and the other, 
to suppose that the acid gas contained in a 
state of union just as much water as was suffi- 
cient to oxidate the metal (this would have 
been thought an extraordinary circumstance 
a few years ago). Either of these positions 
was consistent ; but he adopted the latter, 
and seemed to confirm it by shewing that a 
given quantity of muriatic acid gas afforded 
the same quantity of muriate of silver, whether 
combined previously with potai)h or potaslun]. 


This explanation did not meet my views as 
well as the former, I endeavoured to account 
for the facts (page 289) on the notion of a de- 
composition of the acid. Two circumstances 
conspired to incline me to this view : The one 
was, that hydrogen seemed on other accounts 
to be a constituent of muriatic acid j the other 
was, that water does not ap,.ear in any other 
instance to be combined with any elastic fluid; 
I mean in such way that if the water be re- 
moved, the rest of the molecule will carry 
along with it the character of the whole. In 
one respect I mistook the data, having over- 
rated the weight of muriatic acid gas. — I 
would now be understood to abandon the ex- 
planation founded on the decomposition of the 
acid ; and to adopt the much more simple one 
that the muriatic acid combines with the pot- 
ash of the potasium, at the same instant ex^ 
pelling the hydrogen; in this way there is no 
occasion for any water either combined" or 
olherwise. It exceeds my comprehension how 
Gay Lussac and Thenard should insist so 
largely on the opinion that muriatic acid gas 
contains water, and that principally, as it 
should seem, in order to account for the hy- 
drogen evolved during the combustion of po- 
tasium, and the supposed oxydation of the 


It has been stated that potasium burns ia 
silicated fluoric acid gas (page 283), the result 
is fluate of potash and some hydrogen. The 
theory of this is not obvious. 

Potasium acts upon ammoniacal gas. Mr. 
Davy found that when 8 grains of the metal 
were fused in ammoniacal gas, between 12f 
and 16 cubic inches of the gas were absorbed, 
and hydrogen evolved corresponding to the 
oxydation of the metal by water, that is, 1 
atom of hydrogen for I atom of potasium. 
The new compound becomes of a dark olive 
colour. By applying a greater degree of heat 
the ammonia is in part expelled again ; but 
part is also decomposed. Gay Lussac and 
Thenard say, that by admitting a few drops 
of water to the compound, the whole of the 
elements of the ammonia are recoverable, and 
nothing but caustic potash remains, Mr. 
Davy affirms the results of the decomposition 
to be somewhat different. It seems pretty 
evident, that in this process two atoms of am- 
monia unite to one of potasium, expelling its 
hydrogen at the same moment, , For, 43 grains 
of potasium would require 12 of ammonia j and 
therefore 8 will require 2^ grains, which cor- 
respond to 12x cubic inches. 


5. Soda. 

Soda is commonly obtained from the ashes 
of plants growing on the sea-shore, particularly 
from a genus called salsola ; in Spain, where 
this article is largely prepared, it is called ba- 
rilla. In Britain, the various species o( fucus 
or sea-weed are burnt, and their aslies form a 
mixture containing some carbonate of soda ; 
this mixture is called kelp. Soda is found ii> 
some parts of the earth combined with car- 
bonic acid, and in others combined with mu- 
riatic acid, as minerals ; and hence it has been 
called the fossil or mineral alkali, to distin- 
guish it from potash or the vegetable alkali. 

To obtain soda in as pure a state as possible, 
recourse must be had to a process similar to 
that for obtaining potash. Pure carbonate of 
soda must be treated with hydrate of lime and 
water ; the carbonate of soda is decomposed ; 
the soda remains in solution in the liquid, the 
carbonic acid unites to the lime, and the new 
compound is precipitated. Afterwards the 
clear liquid must be decanted and boiled 
down ; the water gradually goes off with a 
hissing noise till the soda acquires a low red 
heat, when the alkali and remaining water 
become a tranquil liquid. This liquid may be 

SODA. 493 

run out into molds, &c. when it instantly con- 
geals into a hard mass, and is then to be pre- 
served in bottles for use. If still greater heat 
be applied, the alkali and water are together 
dissipated in white fumes. 

Soda thus obtained is a solid, brittle, white 
mass, consisting of about 78 parts pure soda 
and 22 water per cent, j according to d'Arcet 
(Annales de Chimie, Tome 68, p. 182) the 
alkali is only 72 ; but I believe that is too low. 
With more water, soda may be had in crystals, 
like potash, probably containing 50 or 60 per 
cent, of water. Soda, like potash, is extremely 
caustic ; it is deliquescent, and produces heat 
when dissolved in water. The specific gra- 
vity of fused soda I find to be 2, by pouring it 
into a graduated glass tube. There is some 
reason to apprehend that pure soda, could it 
be obtained, would be specifically heavier than 
potabh, though its ultimate particle is certainly 
of less weight than that of the latter. The 
properties and uses of soda are much the same 
as those of potash ; indeed, the two alkalies 
were long confounded, on account of their re- 
semblances. The compounds into which they 
enter are in many instances essentially difTerent, 
and the weights of their atoms are very un- 
equal. The origin of soda in vegetables is 
somewhat obscure, though it may be derived 


from the muriate of soda in the water of 
the sea. 

The weight of an atom of soda is easily de- 
rived from the many definite compounds which 
it forms with the acids ; It appears to be 28 
limes that of hydrogen. The carbonate, sul- 
phate, nitrate and muriate of soda, are all well 
known salts. From a comparison of my own 
experiments with those of others on the pro- 
portions of these salts, free from water, 1 de- 
duce the following : 

per cent. 

Carbonate of soda 40. !• acid, -}- 59.6 base, as 19 : 28 

Sulphate 34.S ■ 4-^.2 34 : 28 

Kitrate ,57.6 42.4 3S : 2S 

Muriate 44 06. 22 : 28 

These proportions scarcely differ 1 per cent. 
from those of Kirwan and other good autho" 
rities. The numbers 19, 34, 35 and 22 being 
the weights of the respective atoms of acids, 
the number 28 must be the weight of an atom 
of soda. Hence we find that soda is a peculiar 
element, differing from every one we have yet 
determined in weight. From the weight of 
the element soda, it may be suspected to be a 
compound of water, oxygen, or some of the 
lighter elements j but from present appear- 
ances, no such suspicion seems well founded. 
Soda should thcn^ with propriety, be treated 


as an elementary principle. We shall proceed 
to the hydrate, the carbonate, and the hy- 
druret of soda, for reasons which have been 
given under the head of potash. 

6. Hydrate of Soda. 

Soda, in what has till lately been considered 
its pure state, is combined with water. The 
smallest portion of water seems to be one atom 
to one of soda ; that is, 8 parts of water by 
weight to 28 of soda, or 22 per cent, of wa- 
ter. I have not obtained soda purer than that 
of d'Arcet of 72 per cent. ; but it always con- 
tained some carbonic acid and other impu- 
rities, which incline me to conclude that 78 
per cent, would be the highest attainable pu- 
rity ; this may be called the first hydrate : it is 
hard and brittle, and twice the weight of wa- 
ter. The second, third, fourth, and fifth hy- 
drates are, I apprehend, crystalline ; but njy 
experience does not warrant me to decide upon 
their nature ; the sixth, and those with more 
water, are all liquid at the ordinary tempera- 
ture ; their specific gravity is obtained in the 
usual way, and the corresponding quantity of 
real alkali is ascertained by the test acids. 

The following Table for soda, is constructed 
after the manner of that for potash (page 476). 



It will be found moderately accurate ; but I 
could not give it the attention it deserves. 
Nothing of the kind has been published to my 
knowledge j yet, such tables appear to me so 
necessary to the practice of chemical enquiries, 
that I have wondered how the science could 
be so long cultivated without them. 

That solution which will be found most 
convenient for a test, is of the specific gravity 
1.16 or 1.17, and contains 14 per cent, by 
measure of real alkali i consequently, 100 mea- 
sures require the same volume of acid tests for 
their saturation. 

Table of the quantity of real soda in watery solutions of 
diflerent specific graviiiti, &c. 




per cent. 

per cent. 




oda. 'A'atcr. 

by weight 

by measure. 




I + 






1 + 1 





red hot 

1 + 2 






1 + 3 

53. S 





1 4- 4 






1 + 5 






1 + 6 




265 « 



J. 47 

















228 o 


















5 . 




7. Carbonate of Soda. 

The salt I call carbonate of soda^ is to be 
had of the druggists in great purity, under the 
name of purified sub-carbonate of soda. It is 
obtained in the form oF large crystals, contain- 
ing much water ; but when exposed to the air 
for some time, these crystals lose most of their 
water, arid becom.e like flour. I took 100 
grains of fresh crystallized carbonate of soda, 
and exposed it to the action of the air in a 
saucer : In 1 day it was reduced to 80 grains ; 
in 2 days, to 6'1- grains ; in 4 days, to 49 grains j 
in 6 days, to 45 grains ; in 8 days, to 44 grains ; 
and in 9 days it was still 44 grains, had the 
appearance of fine dry flour, and probably 
would have lost no more weight. It was then 
exposed to a red heat, after which it weighed 
37 grains nearly. Now, it is a well established 
fact, that the common carbonate of soda, heated 
red, is constituted of 19 parts of acid and 28 
of soda ; or 40.4 acid and b9.Q base, per cent, 
nearly. Klaproth says, 42 acid, 58 base ; 
Kirwan says, 40. i acid, 59,9 base. It is 
equally well established that the crystallized 
carbonate recently formed in a low tempe- 
rature, contains about 63 per cent, water, as 
above determined. All experience confirms 


this ; Bergman and Kirwan find 64 parts of 
water, Klaproth 62, and d'Arcet 63.6. Hence 
the constitution of the crystallized carbonate 
is easily ascertained ; for, if 37 : 63 : : 47 
(= 19 + 28) : 80, the weight of water attached 
to each atom of the carbonate ; that is, 10 
atoms of water unite to 1 of carbonate of soda 
to form the common crystals. Again, if 47 : 
8 : : 37 : 6.3 = the weight of water attached 
to 37 parts of carbonate of soda, to correspond 
with 1 atom of water ; but 37 + 6.3 = 43.3 ; 
from this it appears that 100 parts of crystal- 
lized carbonate being reduced to 44 or 43.3, 
indicates that all the 10 atoms of water are 
evaporated, except one. It should beem, then, 
that the ordinary efflorescence of this salt is not 
dry carbonate, but 1 atom of carbonate and 1 
of water. This supposition is confirmed by ex- 
perience ; for, in 5 days the above 37 grains of 
heated carbonate became 44 grains by ex- 
posure to the air. 

There is another very remarkable character 
of the carbonate of soda, which, however, I 
apprehend will be found to arise from a ge- 
neral law in chemistry j when a quantity of 
common crystallized carbonate is exposed to 
heat in a glass retort, as soon as it attains a 
temperature about 150**, it becomes fluid as 
\^'ater; but when this fluid is heated to 212% 


and kept boiling a while, a hard, small grained, 
salt is precipitated from the liquid, which, 
upon examination, I find to be {\\q fftli hy- 
drate, or one atom of carbonate of soda united 
to 5 atoms of water. For, 100 grains of this 
salt lose 46 by a red heat ; but 1 atom of car- 
bonate weighs 47, and 5 atoms of water weigh 
40, together making 87 j now, if 87 of such 
salt contain 40 water, 100 will contain 46. — > 
The clear liquid resting upon the fifth hydrate 
has the specific gravity 1.35; on cooling, the 
whole liquid crystallizes into a fragile, icy mass, 
which dissolves with a very moderate heat. 
This appears by the test acid to be constituted 
of 1 atom of carbonate and 15 atoms of water. 
Thus the tenth hydrate, by heat, is resolved 
and converted into the fifth and fifteenth ; in 
like manner, probably, the fifteenth might be 
transformed into the tenth and thirtieth hy- 
drate. When any solution below 1.35 sp. 
gravity is set aside to csystajlize, the fifteenth 
hydrate is formed in the liquid, and finally the 
residuary liquid is reduced to the sp. gravity of 
1.18, By treating this liquid solution with 
the test acids, it will be found to consist of I 
atom of carbonate^ to 30 of water. It is of 
course that solution which the common crys- 
tals of carbonate always form, when duly agi- 
tated with water ; or a saturated solution at 

500 FIXED Alkalies, 

the mean ordinary temperature of the atmo- 
sphere. By heat, other liquid solutions may 
be obtained from 1.85 to 1.35 ; but they soon 
crystallize j such may be called supersaturated 

The different species of hydrates in crystals 
have different specific gravities, as might be 
expected; that of the fifteenth is 1.35, that 
of the tenth is 1.42, and that of the fifth 1.64. 
These were found by dropping the crystals 
into solutions of carbonate of potash till they 
were suspended, or by weighing them in sa- 
turated solutions of the same. I could not 
ascertain that of the pure carbonate and the 
first hydrate. 

AVhen carbonate of soda is used for a test 
alkali, the specific gravity 1.22 would be that 
solution which contains 14 per cent, by mea- 
sure of alkali, of which 100 measures would 
require 100 of test acid for saturation ; but, as 
that solution cannot be preserved without par- 
tial crystallization, it will be better to substitute 
a solution of half the strength ; namely, that of 
1.11 ; then 200 measures of the solution will 
require 100 of test acid. 

The following Table contains the characters 
of various combinations of carbonate of soda 
and water, resulting from my investigations. 



Table of the quantit)' of real carbonate of soda in watery 
compounds of different specific graviiies. 




Carb. Soda 

Carb. Soda 

per cent. 

per cent. 




by weight. 

by measure. 



Soda. Water. 

I + 





i + 1 

1 + 5 
1 +10 









1 +15 





1 +20 



1 20 

1 +30 



1 10 



The state of the carbonates in the above 
table it may be proper to notice. The pure 
carbonate is in the state of a dry powder ; so 
is the first hydrate, not to be distinguished in 
appearance from the pure carbonate. The 
fifth hydrate may be obtained in a crystalline 
mass, by hearing the common carbonate till 
a proper portion of water is driven off. Its 
specific gravity is then easily found. The 
tenth hydrate is the common carbonate of the 
shops in crystals. The fifteenth hydrate may 
be had either in a liquid or solid form, as has 
been observed. The twentieth hydrate is a 
liquid without any remarkable distinction that 
I have discovered. It is liable to partial crys- 
tallization. The thirtieth hydrate is a liquid, 
being the saturated solution at common tern- 


perature ; this would probably wholly crys- 
tallize at no very reduced temperature. The 
'2d, 3d, 4th, 6th, &c. hydrates, I have not 
found to offer any remarkable discrimination. 

8. Sodiumy or Ilydruret of Soda, 

According to the present state of our know- 
Jedge, the account of sodium given at page 
262, will require some modification. As the 
article from which sodium has always been 
obtained is the first hydrate of soda, and as in 
the electrization of fused hydrate of soda, no 
gas is given out, according to Mr. Davy, but 
oxvgen ; it follows of course that sodium must 
be a compound of soda and hydrogen, which 
may be called a hydruret of soda. Mr. Davy, 
conceiving soda in a state of fusion to be pure 
or free from water, as was the common opinion 
at the time, concluded that in the electrization 
of it the soda was decomposed into sodium 
and oxygen. This conclusion does not now 
appear to be tenable, though Mr. Davy still 
adheres to it, without having shewn what be- 
comes of the water acknowledged to be pre- 
sent in every instance of the formation of so- 
dium and potasium (Philos. Trans. 1809), to 

SODIUM. 503 

the amount of IG per cent, upon the com- 

Though Mr. Davy's original method of ob- 
taining sodium by Voltaic electricity is the 
most instructive, as to the nature of the new 
product, yet, that of Gay Lussac and Thenard 
is the most convenient when a quantity ot the 
article is required. That is, to pass the vapour 
of red hot hydrate of soda over iron turnings 
in a gun barrel, heated to whiteness. The 
hydrate seems to be decomposed in two ways ; 
in part it is resolved into sodium, or hydruret 
of soda, and oxygen, the former of which dis- 
tils into a cooler receptacle of the barrel, and 
the latter unites to the iron ; in part, the hy- 
drate is decomposed into water and soda, and 
the former again into oxygen, which unites to 
the iron, and hydrogen which escapes, whilst 
the soda unites to the iron or its oxide, forming 
a white metallic compound. 

The specific gravity of sodium is stated by 
Mr. Davy at .9348. The weight of its ulti- 
mate particle (being I atom of soda and 1 of 
hydrogen) must be 29, and not 21, as stated 
at page 263. Consequently, 100 parts of the 
first hydrate of soda, or fused soda, contain 
80.6 sodium and 19.4 oxygen per cent. This 
agrees with that one of Mr. Davy's experi- 
ments which gave the least portion of oxygen. 

504 EARTHS. 

Sodium amalgamates with potasium, ac- 
cording to Gay Lussac and Thenard, in va- 
rious proportions, and the alloys are more 
fusible than either of the simple metals, being 
in some cases liquid at the freezing point of 
water. In general, the properties of sodium 
are found to agree with those of potasium so 
nearly, as not to require distinct specification. 



The class of bodies called earths by chemists 
are nine in number ; their names are Lime, 
Magnesitty Barijtes, Strontites, Alumine or 
Argily Silex, Yttria, Glucine and Zircone. 
The three last are recently discovered and 

The earths constitute the bases of the fossil 
kingdom. Though they have frequently been 
suspected to be compound bodies, and several 
attempts have been made to decompose them, 
it does not yet appear but that they are simple 
or elementary substances. Some of the earths 
possess alkaline properties; others are without 
such properties ; but they all partake of the 
following characters : 1. They are incombus- 

LIME. 505 

tible, or do not unite with oxygen ; 2. they 
are inferior to the metals in lustre and opacity ; 
3. they are sparingly soluble in water ; 4. they 
are difficultly fusible, or resist great heat with- 
out alteration ; 5. they combine with acids j 
6. thev combine with each other, and with 
metallic oxides; and, 7. their specific gravities 
are from 1 to 5 

The latest attempt to decompose the earths 
is that of Mr. Davy ; he seems to have shewn, 
that some of the earths are analogous to the 
fixed alkalies, in respect to their properties of 
forming metals ; but these metals, like those of 
the alkalies, are most probably compoijnds of 
hydrogen and the respective earths. 

1. L 


This earth is one of the most abundant ; it is 
found in all parts of the world, but in a state 
of combination, generally with some acid. 
When united with carbonic acid, it exists in 
large strata or beds in the form of chalk, lime- 
stone, or marble ; and it is from some of these 
that lime is usually obtained. 

The common method of obtaining lime, is 
to expose pieces of chalk or limestone in a kiln 
for a few days to a strong red or white heat ; 
by this process, the carbonic acid is driven off, 

506 EARTHS. 

and the lime remains in compact masses of 
nearly the same si^e and shape as the lime- 
stone, but with the loss oF^lhs of its weight. 
It is probable, the intermixture of the lime- 
stone and coal in the combustion of the latter 
contributes, along with the heat, to the de- 
Composition. The lime from chalk is nearly 
pure ; but tiiat from common limestone con- 
tains from 10 to 20 per cent, of foreign sub- 
stances, particularly aluminc, silex, and oxide 
of iron. 

Lime thus obtained, which is commonlv 
called (juicklinie, is white and moderately hard, 
but brittle. Its s[)ecific gravity, according to 
Kirwan, is 2.3. It is corrosive to animal and 
vegetable substances ; and, like the alkalies, 
converts coloured vegetable infusions, parti- 
cularly blue, into green. It is infusible. It 
has a strong attraction lor water, so as to rob 
the atmosphere of its vapour ; when exposed 
to the atmosphere, it gradually iniblbes water, 
and in a few days falls down into a fine white 
dry powder; in this process, if pure, it ac- 
quires 'i'i per cent, in weight ; after this, it 
begins to exchange its water for carbonic acid, 
and carbonate of Jime is slowly regenerated. 
When 1 part of water is thrown upon 2 of 
quicklime, the lime quickly falls to powder 
with intense heat, calculated to be 800" (page 

LIME. 507 

89) ; this operation is called slaking the lime, 
and is preparatory to most of its applications ; 
the new compound is denominated hydrale of 
limey and appears to be the only proper com- 
bination that subsists between lime and water. 
By a red heat the water is driven off and the 
lime remains pure. 

As lime combines with the principal acids 
hitherto considered, and forms with them per« 
fectly neutral salts ; and as the proportions of 
these salts have been experimentally ascertained 
with precision, we are enabled to determine 
the weights of an atom of lime : thus, 

Acict. Base. 

Carbonate of !ime, 44 -4-56 percent as 19:24 

Siiipliate ■ 5S.5-f4l.4.. 34:24, 

:Nilrale 6l.3-}-3S.7 38:24 

Muriate • 47.S-fJ2.2 22:24, 

Carbonate of lime is, I believe, universally 
allowed to contain either 44 or 45 per cent, of 
acid ; and sulphate is mostly supposed to con- 
tain 58 per cent, acid, the extremes being 56 
and 60. The proportions of the other two 
salts have not been so carefully determined , 
but it is easy to satisfy one's self that the pro- 
portions assigned are not wide of the truth. 
Let 43 grains of chalk be put into 200 grain 
measures of the test nitric acid (1.143), or the 

508 EARTHS. 

test muriatic (1.077), and it will be found that 
the lime will be wholly dissolved, and the 
acids saturated. Hence it follows that the 
elementary atom of lime weighs 24. I have 
formerly stated it at 23, supposing carbonate of 
lime to be, according to Kirwan, 45 acid 4- 55 
lime per cent. The difference is scarcely 
worth consideration ; but experience seems to 
warrant 24 rather than 23 for the atom of 

When a large quantify of water is thrown 
upon a piece of quicklime, it sometimes re- 
fuses to slake for a time j perhaps this is caused 
by the water preventing the rise of tempera- 
ture. In this case the water does not dissolve 
the lime -, hence it should seem that lime pro- 
perly speaking is not soluble in water ; but 
hydrate of lime is readily soluble, though in a 
small degree. The solution is called limc- 
zvate?', and is a very useful chemical agent. 

Lime-water may be formed by agitating a 
quantity of hydrate of lime in water; distilled 
or rain water should be preferred. One brisk 
agitation is nearly sufficient to saturate the 
water ; but if complete saturation is required, 
the agitation should be repeated two or three 
times. After the lime has subsided the clear 
liquid must be decanted and bottled for use. 
Authors differ as to the quantity of lime dis- 

LIME. 509 

solved by water : some say that water takes 
-5-^ of its weight of lime ; others, -g-i-^. The 
fact is, that few have tried the experiment 
with due care. Dr. Thomson, in the 4th ed. 
of his chemistry says, from his experience, -^l-j-. 
This is much nearer the truth than the other 
two. One author says, that water of 212° 
takes up double the quantity of lime that v^ratcr 
of 60° does, but deposits the excess on cool- 
ing : no experimental proof is given. If he 
had said half instead of double, the assertion 
would have been nearly true. I haye made 
some experiments on this subject, and the re- 
sults are worth notice. 

When water of 60° is duly agitated with 
hydrate of lime, it clears very slowly ; but a 
quantity of the lime-water may soon be passed 
through a filter of blotting paper, when it be- 
comes clear and fit for use. I found 7000 
grains of this water require 75 grains of test 
sulphuric acid for its saturation. Consequently 
it contained 9 grains of lime. If a quantity of 
this saturated water, mixed with hydrate of 
iime, be warmed to 130° and then agitated, it 
soon becomes clear ; 7000 grains of this water 
decanted, require only 60 grains of test sul- 
phuric acid in order to produce saturation. 
The same saturated lime-water was boiled with 
bvdrate of iime for two or three minutes, and 

510 EARTHS. 

set aside to cool without agitation ; it very soon 
cleared, and 7000 grains being decanted, re- 
quired only 46 grains of test acid to be neu- 
tralized, the test acid being as usual 1.134. 
Hence we deduce the following table. 

I part 
water of 

60° - 
130° - 
212° - 

takes lip 


es up of dry 

of lime 


latc uf lime 

1 _ 


■ TTJ 










This table leads us to conclude that water 
at the freezing temperature would take nearly 
twice the quantity of lime that water at the 
boiling temperature takes ; I had not an op- 
portunity to try this in the season of these ex- 
periments i but I am informed the calico- 
printers find a sensible difference in lime-water 
in different seasons of the vear, and that in 
winter it is most subservient to their purpose, 
and least so in summer. As water takes up so 
small a portion of lime, and cold water more 
than warm, one would suppose it was the ef- 
fect of suspensioji rather than solution. With 
this view I tried whether the addition of a little 
gum to the water would not increase its solvent 
power ; but the result was, that water of 60* 
took precisely the same quantity of lime, whe- 
ther with or without gum. 1 found that a 
deep earthen vessel which had stood some 

LIME. 511 

months with lime-water exposed to the air, 
still contained -^-^r^ of its weight of lime. 

Lime-water has an acrid taste, notwith- 
standing the small quantity of lime. It operates 
on colours like the alkalies. Certain blue co- 
lours, such as syrup of violets, are changed to 
green ; infusion of litmus, which has been 
converted from blue to red by a little acid, 
has its blue colour restored by lime-water, and 
archil solution, reddened by an acid, is restored 
to its purple colour by lime-water. When ex- 
posed to the air, lime-water has a thin crust 
formed on its surface ; this is carbonate of 
lime, the acid being derived from the atmo- 
sphere ; it is insoluble, and falls to the bottom j 
in time the whole of the lime is thus converted 
into carbonate, and the water remains pure. 
If a person breathes through a tube into lime- 
water, it is rendered milky through the forma- 
tion of carbonate, or if water containing car- 
l)onic acid be poured into it j but a double 
quantity of the acid forms a supercarbonate of 
lime, which is soluble in a considerable degree. 
Though lime is soluble in water in so small a 
quantity, yet a portion of distilled water may 
be mixed with ^ |^ of its bulk of lime-water, 
and the presence of lime will be shewn by the 
test colours, or by nitrate of mercury, &c. 

Lime combines Vv^ith sulphur and with phos- 

512 EARTHS. 

phorus : these compounds will be considered 
under the heads of sulphurets and phosphurets. 
It combines also with the acids, and forms 
with them neutral salts. Lime unites to certain 
metallic oxides, particularly those of mercury 
and lead ; but the nature of these last com- 
pounds is not much known. 

One of the great uses of lime is in the for- 
mation of mortar. In order to form mortar, 
the lime is slaked and mixed up with a quan- 
tity of sand, and the whole well wrought up 
into the consistence of paste with as little water 
as possible. This cement, properly interposed 
amongst the bricks or stones of buildings, gra- 
dually hardens and adheres to them so as to 
bind the whole together. This is partly, per- 
haps principally, owing to the regeneration of 
the carbonate of lime from the carbonic acid 
of the atmosphere. The best ingredients and 
their proportions to form mortar for different 
purposes, do not seem yet to be well un- 

2. Magtiesia. 

This earth is obtained from a salt now called 
sulphate of magnesia, which abounds in sea- 
water and in some natural springs. According 
to the bjest analyses, crystallized sulphate of 


magnesia consists of 56 parts of pure dry sul- 
phate, and 44 parts water in the hundred. 
Some authors find more water in this salt ; 
namely, from 48 to 53 per cent. ; but Dr. 
Henry, in his analysis of British and foreign 
salt, in the Philos. Trans. 1810, takes notice 
of a crystallized sulphate of magnesia contain- 
ing only 44 per cent, water; and the specimen 
of sulphate which I have had for many years 
bears the same character. I am, therefore, 
inclined to adopt this as the true proportion of 
water. Now, Dr. Henry found that 100 grains 
of the above sulphate of magnesia produced 
111 or 112 grains of sulphate of barytes; and 
it is well established that 4 of this last salt is 
acid ; hence, the sulphuric acid in 100 sul- 
phate of magnesia (56 real) is equal to 37 
grains ; consequently the magnesia is equal to 
19 grains: but the weight of an atom of sul- 
phuric acid is 34 ; therefore, 37 : 19 : : 34 : 17, 
nearly, which must be the weight of an atom 
of magnesia, on the supposition that sulphate 
of magnesia is constituted of one atom of acid 
united to one of base, of which there is no 
reason to doubt. I have in the first part of 
this work, page 219, stated the weight of mag- 
nesia to be 20 ; it was deduced chiefly from 
Kirwan's analysis of sulphate of magnesia ; but 

514 EARTHS. 

from present experience I think it is too high. 
Though few of the salts of magnesia have been 
analyzed with great precision, yet the weight 
of the atom of magnesia derived from different 
analyses would not fall below 17, nor rise 
above "20. Dr. Henry and I analyzed the 
common carbonate of magnesia well dried in 
100", and found it to lose 40 per cent, by acids, 
and 57 per cent, by a moderate red heat. Hence 
it should consist of 43 magnesia, 40 carbonic 
acid, and 17 water. We found the carbonate 
begin to give out water and some acid about 
430° ; but it supported a heat of 550° for an 
hour without losing more than 16 per cent. 
Hence the carbonate must be constituted of 1 
atom of acid, 1 of magnesia, and 1 of water, 
stating the magnesia at 20 ; for, 19 + 8 4- 20 
= 47 ; and if 47 : 19, 8, and 20 : : 100 : 40, 
17 and 43 respectively, according to the above 
experirnents. 1 have reason to think, however, 
that the weight of the atom of magnesia ought 
rather to be deduced Irom the sulphate than 
the carbonate ; because it is probable that this 
last always contains a small portion of sulphate 
of lime, when prepared by the medium of 
common spring water; this portion will be 
found in the result of the analysis by fire, and 
will be placed to the account of magnesia. 


Wherefore 1 conclude the weight of an atom 
of magnesia to be 17. It is said that a super- 
carbonate of magnesia is obtainable ; but when 
sulphate of magnesia and supercarbonate of 
soda in solution are mixed together, there is a 
great effervescence and disengagement of car- 
bonic acid, and nothing but the common car- 
bonate of magnesia is precipitated according 
to my experience. Dr. Henry, indeed, ob- 
tained a crystallization by exposing a dilute 
mixture for some time j the crystals were small 
opake globules, about the size of small shot ; 
but upon examination, they proved to be no- 
thing but carbonate of magnesia united to 3 
atoms of water instead of 1 atom. For, 100 
grains lost 70 by a red heat, and 30 by acids ; 
whence its constitution was 30 acid + 30 earth 
+ 'iO water, or 19 acid + 19 earth -f- 24 or 25 
water. The constitution of crystallized sul- 
phate of magnesia must, therefore, be 1 atom 
of acid + 1 atom of magnesia + 5 atoms of 
water ; in weight 34-+17 + 40 = 91; this 
gives per cent. 37 acid + 19 base + 44 water, 
agreeably to Dr. Henry's experience above- 

The constitution of the most common salts 
of magnesia, in their dry state will, therefore, 
be as under - 

516 EARTHS. 

Acid. Base. 

Carbonate of magnesia 53 + 17 percent, as 19 : 17 

Sulphate G6.7 -f- 3:>.3 3-1- : 17 

Nitrate 69 4- 31 38 : 17 

Muriate 5G.4 + 43.6 22:17 

The nitrate of magnesia in the above table 
agrees with that of Kirwan, and Richter, and 
the muriate with that of Wenzel. 

To obtain magnesia, the sulphate must be 
dissolved in water, and a quantity of pure pot- 
ash in solution must be added ; the magnesia 
is then thrown down, and may be separated 
by filtration. Or if carbonate of potash be put 
into the solution of sulphate of magnesia, car- 
bonate of magnesia will then be precipitated, 
which may be separated by filtration ; this last 
must be exposed to a red heat to drive off the 
carbonic acid ; the former need only to be 
dried in a gentle heat. 

Magnesia is a white, soft powder, possessing 
little taste and no smell ; its specific gravity is 
said to be 2.3. It operates on vegetable co- 
lours like lime and the alkalies. It is infusible 
by heat, and very sparingly soluble in water. 
According to KirV\'an, it requires 7000 times 
its weight of water to dissolve it ; I found it 
require 16,000 times its weight of water in 
one experiment. When exposed to the air. 



luagnesia, like lime, attracts 1 atom of water 
to 1 of magnesia, amounting to about 47 per 
cent, by my experience ; it attracts carbonic 
acid but very slowly. It does not combine 
with any ot the simple substances, except per- 
haps hydrogen and sulphur. With the acids it 
forms neutral salts, which are found frequently 
to combine wiih other salts. 

As the sulphate of magnesia is the ordinary 
combination of this earth exhibited as a soluble 
salt, it may be of use to have ? table shewing 
the quantity of real dry sulphate, and of ordi- 
nary crystallized sulphate, in given weights or 
measures of solutions of different specific gra- 
vities. The table is founded on my own ex- 

Table of sulphate of magnesia. 


Dry sulphate 

Dry sulphate of 

Common crystal- 

Mag. Water. 

of magnesia 
per cent, by 

magnesia per cent, 
by me»«urc. 

lized sulphate of 
mag. per cent, by 

specific (f-avitv 

1 + 


1 + 5 




1 66 sol 

1 + 8 




1.50 liq 

1 +10 





1 +15 









42 8 











The fifth hydrate is the ordinary crystallized 
sulphate j the eighth is the strongest liquid so- 

518 EARTHS. 

lution obtained by boiling ; and the fi^eenth is 
a saturated solution at 60". 

3. Biijyles. 

The earth now denominated baryteSy was 
discovered by Scheele in IT?!. Since then 
the labour and experience of several distin- 
guished chemists have added much to the 
knowledge both of the earth and its com- 
pounds ; so that now it may perhaps be said 
to be the best understood of ail the earths. It 
occurs most frequently in combination with 
sulphuric acid, the compound being called 
sulphate of barytes^ formerly ponderous spar, 
and is found about mines, particularly of cop- 
per. It also occurs in combination with car- 
bonic acid, though rarely ; the compound is 
denominated carbonate of barytes. 

Barytes may be obtained either from the sul- 
phate or the carbonate. The former must be 
pulverized, mixed with charcoal, and exposed 
in a crucible to a red heat for some hours ; the 
sulphate is thus changed into a sulphuret. This 
sulphuret is to be treated vvith nitric acid, 
when the sulphur is thrown down, and the 
barytes combines with the acid ; the acid may 
then be driven off by a red heat- and barytes 
will remain in the crucible. If the carbonar<* 


be used, it must be pulverized, mixed with 
charcoal, and exposed for some time in a cru- 
cible to the heat of a smith's forge. Boiling 
water will then dissolve the pure barytes, leav- 
ing the charcoal and carbonate, and upon 
cooling, crystals of hydrate of barytes are ob- 
tained. The greatest part of the water may 
be driven off by heat. 

Pure barytes obtained by the former method 
is a greyish white body, easily reduced to 
powder. It has a harsh and caustic taste, and 
if swallowed proves poisonous. Like lime, 
when exposed to the atmosphere, it absorbs 
water, and then parts with it for carbonic 
acid. It changes certain vegetable blues to 
green. Its specific gravity is nearly 4. Ba- 
rytes forms various combinations with water, 
called hydraUSy which will presently be men- 
tioned. It combines with sulphur and phos- 
phorus, but not with the other simple sub- 
stance. The sulphuret and phosphuret will 
be considered under their respective heads. 
The weight of the ultimate panicle of barytes 
can be very nearly approximated, and appears 
to be 68. or twice the weight of an atom of 
sulphuric acid. This appears from the follow- 
ing statement of the proportions of the most 
common bcrytic salts, which have been suc- 
cessfully investigated. 

520 EARTHS. 

Acid. Btte. 

Carbonate of barytes 22 -f- 78 percent is 19 : 68 

Sulphate 33.3 -f 66.7 3J- : 6S 

Nitrate 36 + 6i 38 : 68 

Muriatft 24.4. + 75.6 22 : 68 

The following respectable authorities agree 
in assigning 22 per cent, acid to carbonate of 
barytes ; namely, Pelletier, Clement, Desor- 
jnes, Klaproth, and Kirwan j and more re- 
cently Mr. Aikin finds 21.67, and Mr. James 
Thomson, 21.75 (Nicholson's Journal, vol. 22 
and 23, 1809). The last mentioned chemist 
finds sulphate of barytes to be 33 acid, and 67 
barytes. His conclusion corroborates the pre- 
vious ones of Withering, Black, Klaproth, 
Kirwan, Bucholz, and Berthier, who all fi:c 
the acid at or near 33 per cent. Vauquelin, 
Rose, Berthollet and Thenard. and Clement 
and Desormes find 32 or more acid j and Four- 
croy and Aikin, 34. It is very satisfactory to 
see the near coincid<»nce in regard to the con- 
stitution of this salt ; because it is frequently 
made a test of the quantity of sulphuric acid 
and of sulphur. Mr. J. Thomson finds 59.3 
barytes per cent, in nitrate of barytes, Clement 
and Desormes 60, Kirwan 58 and 55 at dif- 
ferent trials, and Fourcroy and Vauquelin 50. 
These results differ considerably from each 
other, and are all below the proportion as-r 


signed above ; but it must be observed that 
crystallized nitrate of barytes contains water, 
and perhaps various quantities of water ac- 
cording to the temperature in which it crystal- 
lize'". ; now, if the atom of nitrate be associ- 
ated with 1 atom of water, then the proportion 
of barytes per cent, will be 59.6, which nearly 
agrees with Thomson, and Clement and De- 
sormes ; if with 2 atoms of water, the barytes 
will be 55,7 percent, j if with 3 atoms, then 
52.3, 8ic. — Crystallized muriate of barytes ap- 
pears clearly to consist of an atom of dry mu- 
rjate + 2 atoms of water , or 22 acid •+- 68 
barytes + 16 water; this reduced gives 20.8 
acia + 64.1 barytes + 15.1 water per cent. — 
For, Kirwan finds 20 acid + 64 base +16 
water j Fourcroy, 24 acid + 60 base + 16 wa- 
ter; and Aikin, 22.9 acid + 62.5 base + 14.6 
water per cent., which agree with each other, 
and with the theory as nearly as can be ex- 

Rarytes combines with most acids, and forms 
with them neutral salts. In many respects it 
appears to be related to the fixed alkalies, only 
in weight it is nearly the same as both of them 
put together. 

522 EARTHS. 

Hydrate of Barytes. 

When pure barytas, obtained from the ni- 
trate by heat, is exposed to the air, or is moist- 
ened by water, it combines with it, and that 
in various degrees, forming a number of Aj/- 
drates, which have not been sufficiently at- 
tended to and discriminated ; much heat is 
evolved during the combination : it was mis- 
taking the first hydrate of barytes for pure ba- 
rytes that caused the uncertainty for some time 
in regard to the proportions of the elements of 
sulphate of barytes (see page 474). Now, if 
an atom of barytes weigh 68, the first hydrate 
will weigh 76, to which if 34 sulphuric acid 
be added, we shall have an atom of sulphate 
of barytes = 102, (for the water is driven off 
by the union of the acid and base) ; if then we 
conceived the hydrate to be pure barytes, we 
should conclude that 76 barytes united to 26 
sulphuric acid to form 102 sulphate, which is 
very near the former mistaken conclusion of 
Thenard and Berthollet. Hence, then, there 
is reason to conclude that their barytes, kept 
some time in a red heat, was in reality the first 
hydrate, or one atom of barytes and one of \n^- 
ter. When pure barytes is dissolved in boiling 
water, a solution is formed of specific gravity 



-•xceeding 1.2; on cooling, great part of it 
crystallizes ; these crystals are the tzventietk 
hydrate, or consist of 1 atom of barytes and 20 
of water, or 30 barytes and 70 water per cent. ; 
if they are exposed to a heat about 400" or 5(X)% 
they melt, great part of the water is dissipated, 
and a dry whiie powder is obtained, which is 
iht Jifth hydrate. In this operation, 223 parN 
(r= 6^ -f 20 X 8) are reduced to 108 (= 68 -h 
5 X ^), or 100 to 47, which is exactly the re- 
duction obtained experimentally by Dr. Hope, 
This dry powder melts below a red heat ; but 
I have not been able to find what it would be 
reduced to by exposure to a red heat, because 
it acquires carbonic acid, even in a crucible, 
as Benhollet has observed, almost as fast as it 
loses water. My experience on the crystals of 
barytes has been limited ; but from the follow- 
ing I conclude they are the hvejitieth hydrate. 
1 took 80 grains cf fresh crystallized barytes, 
and dissolved them in 1000 grains of water-, 
the solution was of the specific gravity 1 .024 ; 
this solution took 70 grain measures of test sul- 
phuric acid to saturate it, and afforded 36 grains 
of dried sulphate of barytes : of this 12 grain;? 
were acid and 24 barytes. AVhence we learn, 
1st, that 80 grains of crystals are equal to 24 
real barytes, or 22.S equal to 68 ; but 228 ~ 
20 X 8 + 68, which shews that 20 atoms <:t 



water are united to 1 of barytes; 2d^ that the 
decimals in the second and third places of the 
expression for the specific gravity, denote the 
ouantity of real barytes in 1000 grain measures 
of the solution. This last must evidently hold 
witViont anv material error in all the niferior 
solutions ; and hence the strength and value of 
barytic water may be known by its specific 
gravity, an advantage which does not practi- 
cally appertain to lime-water. By subsequent 
trials, however, I found the quantity of barytes 
rather overrated. 

The following sketch of a table of the hy- 
drate of barytes may have its use, till a more 
ample and correct one can be constructed. 

Table oftlie Hydrate of Barytef;. 


Barytes per 

Barytes per rcrt. 

Biryt. Water. 

cent, by 

by measure. 

Specific e"*"'!'' 

Congealing point 

1 + 


400 ? 

4 00? sol. 


1 + 1 



1 + 5 

I -f 20 



1.6 — 


1 + S(i 



1.3 fl. 


1 + 27.5 



1.03 — * 

40° ? 





1. 01 — 

4. Strontites. 

The mineral from which this earth is ob- 
tained was first found in the lead-mine of Stron- 
tian in Argyleshire, Scotland. The earth and 

* This is a saturated solution in the mean temperature 
of ec. 


its distinguishing properties, were pointed out 
by Dr. Hope in an essay read to the Royal 
Society of Edinburgh, in 1792, and published 
in their Transactions, 1794. Several distin* 
guished chemists have since confirmed and ex* 
tended these investigations. The Scotch mi- 
neral is a carbonate of strontites ; but the earth 
has since been found in various parts combined 
with sulphuric acid. 

Strontites is obtained from the sulphate or 
carbonate of strontites, by the same processes 
as barytes from the like compounds ; indeed, 
it bears so close a resemblance to barytes, both 
in its free and combined state, as to have been 
confounded with it. Strontites has much the 
same acrid taste as barytes ; but it is not poi- 
sonous ; it is less soluble in water than barytes; 
it has the property of giving a red or purple 
colour to flame, for which purpose the nitrate 
or muriate may be dissolved in alcohol, or ap- 
])lied to the wick of a candle. The weight of 
the atom of strontites is deducible from the salts 
which it forms with the more comnion acids to 
be 46. Thus, 

Acid. Baif. 

Carbonate of strontites 29.2 -f- "'^-^ P^f cent, as 19 : 46 

Sulphate 42.5 + 57.5 34:46 

Nitrate 45.2 + 54.8 38 : 46 

"Muriate ' ^ 32.4 + 67.6 22 46 

52& EARTHS. 

Dr. Hope, Pelletier, and Klaproth find 30 
per cent, of acid in the carbonate. Klaproth, 
Clayfield, Henry, and Kirwan find 42 per cent, 
acid in the sulphate. Kirwan finds the crys- 
tallized nitrate to contain 31.07 acid, 36.21 
base, and 32.72 water; which I presume de- 
notes 1 atom of acid, 1 of base, and 5 of wa- 
ter ; that is, 38 acid + 46 base + 40 water ; 
this reduced, would give 30.6 acid, 37.1 base, 
and 32. S water per cent, which very nearly 
agrees with his experience. Taking the dry 
salt, his results would give 46.2 acid, and 53.8 
base. A'auquelin finds the nitrate to contain 
48.4 acid, 47.6 base, and 4 water; but this 
constitution cannot be correct : Neither can 
Richter's analysis, which gives 51.4 acid and 
water, and 48.6 base.— 'Dry muriate of stron- 
tites, according to Kirwan, consists of 31 acid, 
and 69 base ; but Vauquelin states 39 acid, 
and 61 base ; the former, without doubt, is 
nearer the truth. 

HydnUe of Stroiititcs. When water is put 
to pure strontites, it becomes hot and swells, like 
lime and barytes, and falls into dry powder. 
This powder seems to be the tirst hydrate ; 
whence, 46 parts of strontites will take 8 of 
water to form this combination ; but if more 
water be added, the hydrate crystallizes. 
These crystals appear to be the 12lh hydrate ; 


that Is, they are constituted of 1 atom of stron- 
tites and 12 of water = 46 4- 96 = 142, or 32 
strontites + 68 water per cent, agreeably to 
the experience of Dr. Hope. Water dissolves 
about -r^Trtb of its weight of pure strontites in 
the temperature of 60°, or y^th of its weight 
of the crystals ; the specific gravity of the solu- 
tion is nearly 1.008. But boiling water dis- 
solves about half its weight of the crystals. 
"Whence it appears that strontites is much less 
soluble than barytes, and much more soluble 
than lime. The specific gravity of the crystals 
of strontites is rightly determined by Hassen- 
Iratz to be nearly 1.46. Strontian water may 
be used for the same purposes as lime-water, 
or barytic water. 

Strontites combines with most of the acids to 
form neutral salts. It also combines with sul- 
phur and phosphorus. 

5. Almnine^ or Jrgil. 

The earth denominated alumine, constitutes 
a great portion of common c/aj/ ; but this last 
is a mixture of two or more earths with iron, 
&c., and therefore cannot be exhibited as pure 
alumine. The earth may be obtained pure 
from a common well known salt, called alum, 

528 EARTHS. 

which is constituted of sulphate of potash and 
sulphate of alumine combined together, with 
a portion of water. A quantity of alum is to 
be dissolved in 10 times its weight of water ; 
to this a quantity of liquid ammonia is to be 
added ; the sulphuric acid seizes the ammonia, 
and lets fall the alumine, whicti may be sepa- 
rated from the liquid by filtration ; and then 
exposed to a red heat. 

Alumine thus obtained is a fine white earth, 
spongy, and adhesive when moistened j it has 
neither taste nor smell ; it is said to have the 
specific gravity, 2. When mixed with water, 
it forms a mass which is the basis of earthen 
ware, and capable of receiving any figure, In 
this case, by the application of great heat, it 
becomes excessively hard, and loses in part, 
or wholly, its adhesive quality. Pure alumine 
bears the highest heat of a furnace without un- 
der^joinjr anv change. 

Alumine does not form any known combi- 
nation with oxygen, hydrogen, charcoal, sul- 
phur, or phosphorus ; but it combines with 
the alkalies, with most of the earths, and with 
several metallic oxides. It combines too with 
many of the acids, but forms in most cases un- 
crystallizable salts. It possesses a strong affi- 
nity for vegetable colouring matter, and hence 
its great importance in the arts of dyeing and 

ALUMINE. .^29 

printing, in which it is employed to fix the 
colour on the cloth. 

The weight of an aiom of alumine is not so 
easily determined as that of the preceding 
earths and alkalies ; partly because ihe salts 
which it forms with the acids are not crystal- 
lizable, and partly because they have not had 
a proportionate share of attention paid to them. 
The only salt with alumine which has been 
carefully analyzed is the triple compound, or 
alum ; an acquaintance with the constitution 
and properties of this salt is of great importance 
to its manufacturer, and to the various artists 
to whom it is of indispensible utility. 

The experience of Chaptal, Vauquelln, and 
of Thenard and Roard (An. de Chimie, vol. 
22, 50, and 59, or Nicholson's Journal, vol. 
18) shews that the alum of all countries is very 
nearly the same in its constitution and qualities, 
that it contains 33 percent, sulphuric acid, 11 
or 12 alumine, 8 or 9 potash, and 47 water. 
All the authors I have mentioned do not agree, 
it is tf-ue, in these numbers ; but the differences 
•are more in appearance than reality. V^au- 
quelin obtains 95 sulphate of barytcs from 100 
alum, but Thenard and Roard obtain 100. 
The last mentioned chemists adopt only 26 
per cent, acid in sulphate of barytes ; whereas 
it is now universally allowed there are about 

530 EARTHS. 

33 p)er cent, acid in that salt. Mr. James 
Thomson, I am informed, finds nearly 100 per 
cent, sulphate of barytes. This result I adopt 
as the most correct, and it is also the most 
recent. Vauquelin finds 481- water in alum j 
this is more than is generally found, and ac- 
counts in some degree for his obtaining less 
sulphate of barytes. Chaptal finds 47 per cent, 
water in English alum, with which my expe- 
rience accords. Vauquelin finds 10.5 alumine, 
Thenard and Hoard, 12.5 per cent. Mr. 
Tennant of Glasgow, who favoured mc with 
an analysis, finds 11.2 alumine in the alum 
manufactured there. This last chemist finds 
1 5 per cent, sulphate of potash, which is the 
same as Thenard and Hoard's nearly, 15.7. 
Now, as 34 acid 4- 42 potash, have been 
shewn to constitute 76 sulphate, 15 must con- 
tain 6.7 acid and 8.3 potash. Collecting these 
results then, it appears that alum may be said 
to consist of, 

33 sulphuric acid. 
11.7 alumine. 

8.3 potash. 
47 water. 



Of the 33 sulphuric acid^ it must be recol- 
lected that 6.7 parts beJong to the potash ; that 
is, yth of the whole ; the remainder, or ^tlis, 
belong to the alumine. Hence, then, were 
there only '> atoms of sulphuric acid ui a mole- 
cule of alum, 1 atom would appertain to an 
atom of potash, and the other 4 atoms to as 
many of alumine, provided the acid and alumine 
unite one to one, which we are to presume 
till sufficient reason appear to the contrary. 
It should seem, then, that an atom of alum is 
constituted of one of sulphate of potash in the 
centre, and 4 atoms of sulphate (if alumine 
around it, forminor a square. But S3 — 6.7 
= 26.3 acid to 11.7 alumine; and 26.3 : 11.7 : . 
34 : 15, the weight of an atom of alumine. 
Dry alum must, therefore, be 5 X 34 + 4'2 -f 
4X15= 272 ; but as this is found combined 
with water in the state of common alum, it 
will be satisfactory to know how many atoms 
of water are attached to one atom of dry alum • 
for this purpose, we have 53 : 47 : : 272 : 24 J 
= the wcij^ht of water ; this, divided b)' ^, 
gives the number of atoms = 30. Hence, an 
atom of common alum consists of, 

1 atom of sulphate of potash r= 76= per cent. 15 

4 atoms of sulphate of alumine = I9e 38 

And 30 atoms of water. =240 47 

5!2 100 

532 EARTHS. 

A saturated solation of alum in water, at the 
temperature 60°, is of the specific gravity 1.048, 
and is constituted of 1 atom of dry alum and 
600 of water ; or the alum has 20 times the 
quantity of water that the crystals contain. 
The specific gravity of alum itself is about 1 .7 1 ; 
and by means of heat, solutions of it in water 
may be obtained of any inferior specific gra- 
vity ; at least, I have had a solution, which, 
when hot, was 1.57. 

Alumine does not combine with carbonic 
acid; but it combines with the nitric and mu- 
riatic acids J it would, therefore, be desirable 
that the weight of an atom of alumine should 
be investigated fiom these last combinations, 
as well as from the sulphate. No author that 
I know has given the proportion of elements 
in nitrate of alumine ; and in muriate of 
alumine Bucholz determines equal parts of acid 
and base, and Wenzel 28 acid to 72 base ; so 
that no confidence can be placed in them. 1 
determined the proportions of these salts as 
follows : 100 grains of alum were dissolved in 
water; the alumine was precipitated by 150 
measures, more or less, of test ammonia, {.91), 
care beinsT taken that the aluminous solution 
was saturated with ammonia, and that none 
v;as superabundant ; the liquid was then well 
agitated, and immediatelv divided into three 



equal portions. It was then found that each 
of these portions took 52 measures of the test 
acids.; namely, the sulphuric, the nitric, and 
the muriatic respectively, to dissolve the float- 
ing alumvne, and to clear the solutions which 
were afterwards found to be free from uncom- 
bined acids. Hence, the proportions of the 
salts are deduced as under : 

Acid. Base. 

Sulphate of alumine 69.4 + 30.6 per cent, as 34-: 15 

Nitrate 71.7 + 28.3 38 : 15 

Muriate 59.5 +40.5 22 : 15 

It will be proper here to notice an opinion 
which Vauquelin supported in his essay in 
1797, but which is not adverted to in his suc- 
ceeding essay in 1804, nor in the one of The- 
nard and Roard in 1806; I mean the opinion 
that alum consists of the supersulphate of alu- 
mine and sulphate of potash. If this be true, 
then the atom of alumine must weigh 30, be- 
cause 2 atoms of sulphuric acid unite to 1 of 
alumine. The opinion appears to me without 
support. When a solution of alum is put to 
the blue test, it changes it to red ; but this is 
not a proof of excess of acid where the base of 
the salt has a strong affinity for colouring mat- 
ter ; there is probably a true decomposition of 
the salt, or perhaps the colouring matter forms 

534 EARTHS. 

a triple compound with the salt. Thai no 
uncombined acid accompanies alum is certain, 
because the least portion of alkali decomposes 
it. Besides, a red heat drives off half of the 
acid at least from supersalts ; but alum bears a 
red heat without losing a sensible portion of 
acid. From the experiment related above, it 
appears that the sulphuric, the nitrfc, and the 
muriatic acid tests are of equal efficacy in satu- 
rating alumine. Are thes^ all supersalts ? If 
so, why does not half the acid rn each case 
neutralize the earth, and form a simple salt? — 
But it is said if alumine be boiled in a solution 
of alum, the alumine combines with the alum, 
and falls down an insoluble, neutral salt. 
Vauquelin asserts he has made the experi- 
ment ; but he mentions no proportions, nor 
does he point out the time requisite to produce 
the effect. With a view to this subject, I pre- 
cipitated the alumine from a measure of satu- 
rated solution of alum at 60° (about 100 grains 
of alum) by the necessary quantity of ammonia j 
to this liquid, which was found neutral, still 
containing the alumine in suspension, I put 
another measure of the same solution of alum, 
and boiled the whole for 10 minutes in a glass 
vessel J it was then set aside to cool, and fil- 
tered i the liquid was not much diminished in 
specific gravity, and required nearly the same 

ALUMINE. 5.35 

quantity of ammonia to saturate it, and af- 
forded the same quantity of alumine as the first 
measure. Apprehending the sulphate of am- 
monia present might influence the result, I 
next put the dry pulverized alumine from 100 
grains of alum into a solution of 100 grains of 
alum in water, and in another experiment the 
moist recently filtered alumine, and boiled t\\e 
whole for 10 minutes; the water evaporated was 
restored, and the liquor filtered ; it was of the 
same specific gravity as at first, tasted equally 
aluminous, and the precipitate collected and 
dried, weighed just the same as before. These 
facts lead me to doubt concerning the existence 
of this alum saturatedwith its earthy as the earlier 
chemists called it. But supposing the existence 
of a combination of sulphuric acid with twice 
the quantity of alumine, I know no reason why 
it should not be constituted of 1 atom of acid 
and 2 of alumine. Hence, I conclude the 
weight of an atom of alumine above slated is a 
fair deduction. 

The French chemists seem to have proved 
that the presence of even a very small portion 
of sulphate of iron in alum is very injurious in 
some of its uses in dyeing, Sic. 

Hydrate of Alumine, Saussure, in the 52d 
vol. of the Journal de Physique, observes, that 
alumine is precipitated from its solution, in 

536 EARTHS. 

two very different states, according to circum- 
stances ; the one he calls spongy, and the other 
gelatinous alumine ; they both retain 58 parts 
per cent, of water, when dried in common 
summer heat ; the former parts with the whole 
of its water at a red heat; but the latter only 
loses 48 per cent, at the highest temperature. 
There may be some doubt as to the accuracy of 
these facts ; but it would seem probable that 
alumine, at the ordinary temperature, retains 2 
atoms of water, or 15 parts alumine hold 16 of 
water ; this would allow 52 per cent, loss 
by a red heat. The subject deserves further 

6. Silex. 

The earth denominated silex, is found abun- 
dantly in a great many stones ; it is almost pure 
in Jlinty rock crystal, and others ; but of stones 
in general it only constitutes a part, being 
found in combination with one or more of the 
other earths, or with metals, &c. It is also 
found in small particles in the form of white 
sand. The most distinguishing feature of this 
earth is its melting along with either of the 
fixed alkalies, and forming with them that 
beaulifui and well known compound, glass. 
The specific gravity of flint and rock crystal is 
usually about 2.65. After being heated red 

siLEX. 537 

hot for some time, flint may be pulverized in 
an iron mortar, and forms a white earth, which 
may be regarded as silex suflrtciently pure for 
most purposes. It forms a harsh, gritty pow- 
der, which does not cohere nor form a paste 
with water like clay. It is insoluble in water 
in any sensible degree. It is infusible by heat, 
unless at an extremely high degree. To obtain 
silex in a pure state, a mixture of sulphuric 
acid and fluate of lime must be distilled in glass 
vessels, or along with pulverized flint, when 
superfluate of silex is produced in an elastic 
state ; the gas may be received over water, on 
the surface of which a crust of fluate of silex is 
formed ; this crust being removed by filtration 
or otherwise, the clear liquor is to be saturated 
with ammonia, when pure silex is thrown 
down. When dried in a red heat, it forms a 
fine white powder. The common mode pre- 
scribed to obtain pure silex gives pure glass, as 
will presently be explained. It is remarkable, 
that sulphuric acid, poured on fluate of silex, 
expels the fluoric acid in fumes, though it does 
not combine with the silex. 

Silex combines with the two fixed alkalies, 
with most of the earths, and with metallic 
oxides ; but with few of the acids immedi- 
ately, except the fluoric ; when joined to an 
alkali, it may be united to several of the acids, 

538 EARTHS. 

forming triple salts. It seems not to combine 
with oxygen, hydrogen, or the other combus- 
tibles, nor with ammonia. 

The fixed alkalies may each be combined 
with silex in two proportions. In order to 
form glass, one part of silex and one of fine 
dry carbonate of soda may be mixed together ; 
but if potash is used, then 1^- parts will be re- 
quired. If the other or soluble compound iii 
wanted, then double the quantities of alkali 
must be used, or 2 parts of soda and 3 of pot- 
ash. A strong red heat in each case is acces- 
sary to form a complete union of the principles ; 
the fused mass gives out the carbonic acid of 
the alkalies, and when poured out immediately 
becomes glass; but when the double quantity 
of alkali is used, the glass is deliquescent, and 
may be completely dissolved in water. This 
last may be caHed supersodiuretted or superpo- 
tasiuretled si/ex, and the former sodiurelted or 
potasiurett^d silex. When an acid is dropped 
into a solution of superpotasiuretted silex, a 
white precipitate is immediately formed, which 
is potasiuretted silex, or common glass, and 
not silex, as has hitherto been supposed. For, 
1. The heated precipitate, I find, weighs about 
^ds of the red hot potasiuretted silex, whereas 
the silex is only about -^d of the compound ; 2. 
the acid requisite to throw down the preci- 

SILEX. 531; 

phate, is only half of that which the alkali in 
the compound would require for its saturation ; 
S. the precipitate, dried in a moderate red 
heat, is fusible into glass by the blow-pipe -, 
and, 4. as the acids do not take the alkali 
from glass, they ought not to take more alkali 
from superpotasiurettcd silex than what would 
reduce it to common glass. 

It is more difficult to find the weight of an 
atom of silex than that of any other of the pre- 
vious earths, because it enters into combination 
with only one of the acids, and the proportions 
have not yet been ascertained, i have, how- 
ever, succeeded pretty well by investigating its 
relations with potash, lime, and barytes. Hav- 
ing obtained a quantity of superpotaaiuretted 
silex without any excess of alkali ; that is, 
which afforded a precipitate with the least por- 
tion of acid (for if the alkali be in excess, acid 
may be added without any precipitation), 1 
precipitated a given weight of the dried com- 
pound previously in water, by sulphuric acid 
in excess ; the precipitate was heavy and bulky ; 
after remaining on the filter for some time, it 
resembled a mass of over-boiled potatoe ; the 
water being forced out by pressure, a white 
subtance remained, which easily leff the filter, 
and when dried in a low red heat, left a harsh 
giitty powder, nearly 4ds of the weight of the 

540 EARTHS; 

compound. Again, test sulphuric acid was 
slowly added to the solution, of a given weight 
of the dry compound in water ; as soon as the 
mixture manifested acid to the test liquid, it 
was considered as saturated. The whole acid 
added was found to be sufficient to saturate a 
weight of pure alkali nearly equal to -j-d of that 
of the dry compound. These experiments 
rendered it obvious that only one half of the 
alkali was engaged by the acid, the other half 
remaining with the silex ; and the conversion 
of the precipitate into, glass by the blow-pipe 
confirmed the conclusion. It remainecf, then^ 
to determine which of the two combinations 
of alkali and silex was the most simple. As a 
part of the alkali is easily drawn from one com- 
pound, and difficultly from the other, the 
former must be supposed two atoms of alkali 
to one of silex, and the latter one to one. 
From this it should seem, that the weight of 
an atom of silex is nearly the same as that of an 
^tom of potash ; and the near agreement of 
the specific gravities of these two bodies, is an 
argument in favour of the conclusion. 

Superpotasiuretted silex exhibited remark- 
able results with lime and barytes. One hun- 
dred measures of the solution, containing 18 
grains dry, were saturated with 5000 grains of 
lime water, containing 6 grains of lime -, the 

SILEXi 541 

precipitate, filtered and dried in a low red 
heat, was 19 grains. The residuary liquid re- 
quired 27 grains of test muriatic acid to sa* 
turate it ; whereas, the like quantity of lime 
water took 54 grains. Here, then, it a[)pcars 
that each atom of the superpotasiuretted silex 
must have been decomposed into one atom of 
potash, which remained in the liquidj and one 
atom of potasiuretted silex, which united to 
two atoms of lime, and the compound was pre- 
cipitated. That the matter in the liquid was 
pota«h, and not lime, was proved by carbonic 
acid 9 and the test muriatic acid shewed that 
every atom of potash in the liquid took the 
place of two atoms of lime. The case was 
different with barytes. One hundred measures 
of the solution, containing 18 grains dry, were 
saturated with 850 measures of 1.0115 barytic 
water, containing 9 dry barytes. The resi- 
duary liquid took 28 test acid to saturate it, 
and the precipitate dried in a red heat was 20 
grains. Here it is evident that one atom of 
barytes had detached one of potash from the 
compound, and taken its place ; consequently, 
the residue of liquid required the same quan- 
tity of acid as the barytic water, and the pre- 
cipitate was a triple compound of silex, pot- 
ash, and barytes •, one atom of each, consisting 

5i'2 EARTHS. 

probably ot 9 pans of barytes, 5| silex, and 
5^ potash. 

Upon the whole, I am inclined to believe 
that one atom of silex weighs nearly 45 times 
that of hydrogen. 

Silex combines with alumine by heat, and 
the compound forms hard infusible bodies, such 
as porcelain, earthen ware, bricks, 8jc. 

7. Yttria. 

This earth is found at Ytterby, in Sweden. 
It constitutes a portion of tlie mineral called 
gadolinite, first analyzed by Gadolin, and of 
that called i/lirotajitalite, both found in the 
same mine. The earth may be obtained by 
dissolving the pulverized mineral in a mixture 
of nitric and muriatic acids ; the liquor poured 
off is then evaporated to dryness, the residuum 
dissolved in water. If ammonia be now added, 
the earth is precipitated. It is obtained in the 
form of a white powder, said to be of the spe- 
cific gravity 4. SI. It is infusible by heat, and 
insoluble in water : but it forms salts with se- 
veral of the acids ; and these salts have mostly 
a sweet taste, and are in some instances co- 
loured. They resemble the m. tallic salts in 
many particulars. According to Klaproth, the 


hydrate of yttria, a dry powder, contains 31 
per cent, water ; this would imply that the 
atom of yttria weighs 18, 36, or 53, according 
as it is the first, second, or third hydrate ; but 
he finds the carbonate of yttria to be 18 acid, 
55 yttria, and 27 water: now, supposing the 
carbonate to be I atom of acjd, 1 of earth, and 
3 of water, and that the acid and water weigh 
45, then the atom of earth is deduced to be 
53 ; and this conclusion agrees with tiie pre- 
ceding one, which supposes the hydrate to be 
the third. The great specific gravity of the 
earth countenances the notion of the atom be- 
ing heavy ; but we cannot rely upon the above 
determination till it is supported by more va- 
rious experiments. 

8. Glucine. 

The earth called glucine (from the sweet- 
tasted salts which it forms with acids) is ob- 
tained chiefly from two minerals, the beryl 
and the emerald. These minerals are consti- 
tuted of silex, alumine, and glucine; the two 
former being abstracted by the usual processes, 
there remains the glucine, a soft white powder, 
adhering to the tongue, but without taste or 
smell, and infusible by heat. Its specific gra- 
vity is said to be 2.97. It is insoluble in wa- 

5i4f EARTHS. 

ter. This earth combines with the acids, with 
liquid fixed alkalies, and with liquid carbonate 
of ammonia. In the last case it resembles 
yttria, but is much more soluble than that earth 
in carbonate of ammonia. Glucine has consi- 
derable resemblance in its properties both to 
alumine and yttiia. 

We have not data sufficient to find the 
weight of an atom of glucine ; but from the 
experiments of Vauquelin on the carbonate of 
glucine (Annal. de Chimie, torn. 26, pages 
160 and 172) it should seem to weigh nearly 
30, or twice the weight of alumine. It is re- 
markable, too, that the analysis of the beryl, 
and of the emerald, give nearly the same quan- 
tity of alumine and glucine, which indicates 
thar the weight of an atom of the latter is ei- 
ther equal to that of the former, or some mul- 
tiple of it. 

9. Zircone. 

The zircon or jargon, and the hyacinfhy are 
two precious stones found chiefly in Ceylon. 
These contain a peculiar earth which has re- 
ceived the name of zircone. It may be ob- 
tained ihus : Let one part of zircon in powder, 
be fused with 6 parts of potash ; then let the 
mass be diffused through a portion of water, 



which will dissolve the potash and its combi- 
nations, and leave a residuum. This residuum 
must be dissolved in muriatic acid, and potash 
must be added, which will precipitate the zir- 
cone. It is a fine white powder, insipid, and 
somewhat harsh to the feel. When violently 
heated, it is converted into a kind of porcelain, 
very hard, and of the specific gravity 4.35. 
Zircone is not soluble in water, but it retains 
.|. or -^ of its weight of water when dried in the 
air, and assumes the appearance of gum arable. 
Zircone is not soluble in liquid alkalies, but it 
is in the alkaline carbonates; it adheres to se- 
veral of the metallic oxides. Zircone unites 
with acids, and forms with them salts, many 
of which are insoluble in water, but others are 
very soluble. They have an astringent taste, 
resernbling some of the metallic salts. 

As tne salts of zircone have not yet been 
formed with sufficient care to ascertain the 
ratio of their constituent principles, we can not 
exactly determine the weight of an atom of this 
earth. Vauquelin finds 44 carbonic acid and 
water and 56 zircone in carbonate of zircone ; 
but, unfortunately, he has not given the acid 
separately from the water. Allowing the ac- 
curacy of the above, and supposing the car- 
bonate to contain 1 atom of water, the weight 
of an atom of zircone will be 34 s but if wc 

546 EARTHS. 

suppose 2 atoms of water, then the atom of 
earth comes out 45. This last I judge to be 
nearest the truth. It is remarkable, that the 
hyacinth contains 32 parts of silex and 64 of 
zircone, which, according to the above con- 
clusion, corresponds to 1 atom of silex and 2 
of zircone, a constitution by no means impro- 
bable. Upon this principle, the gummy hy- 
drate above mentioned, may be 2 atoms of 
water and I of zircone, or 16 water + 45 



PLATE 5. Exhibits the various symbols devised to re- 
present the simple and compound elements ; they are nearly 
the same as in plate 4, only extended and corrected : they 
will be found to agree with the results obtained in the pre- 
ceding pages. 

Fig. Simple. 




1. Oxygen 


12. Iron 


2 Hydrogen 


13. Nickel 

25 ? 50 ? 

3. Aziote 


14. Tin 


4. Carbone 


1 5 . Lead 


5, Sulphur 


16. Zinc 


6. Phosphorus 


17. Bismuth 


7. Gold 

140 ? 

18. Antimony 


8. Platina 


19. Arsenic 

42 ? 

9. Silver 


20. Cobalt 

55 ? 

10. Mercury 


21. Manganese 


\\. Copper 


22. Uranium 




Fig. Wt. 

23. Tungsten 5ti ? 

24-. Titanium 40 ? 

25. Orium 45 ? 

26. Potash 42 

27. Soda 28 

28. Lime 24 

29. MagMsia 17 

30. Barytes 68 
81. Strontites 46 

32. Alumine 15 

33. Silex 45 

34. Yltria 53 

35. Olucine 30 

36. Zircone 45 


37. Water 8 
38- Fluoric acid 15 

39. Muriatic acid 22 

40. O.xymuriatic acid 29 

>'g. Wt. 

41. Nitrons pas? 12 

42. Nitrous oxide 17 

43. Nitric acid 19 

44. Oxj'oitric acid 26 

45. Nitrous acid 31 

46. Carbonic oxide 12,4 

47. Carbonic acid IQ.-t 

48. Sulphuroas oxidfe 20 

49. Sulphurous acid 27 

50. S'liphuric acid 34 

51. Pliusphoronsarid 32 

52. Phosphoric acid 23 

53. Ammonia 6 

54. Olefia;n gas 6.4> 

55. Carburett^d hyd. 7.4 
56 Sulphuret. hydr, 14 

57. Supersulph. hydr. 27 

58. Phosphuret. hydr. 10 

59. Phosphor, sulph. 22 

60. Superphos. sulph. 31 

PLATE 6. Symbols of compound elements (continued 
from Plate 5.) 

Fig. Wt. 

1. Hydrate of potash 50 

2. Potasium, or hydro ret 

of potash 43 

3. Carbonate of potash 6 1 

4. Hydrate of soda 36 

5. Sodium, or hydruret 

of soda 29 

6. Carbonate of soda 47 

7. Hydrate of lime 32 

8. Carbonate of lime 43 

9. Sulphate of lime 58 

10. Nitrate of lime 69, 

11. Muriate of lime 46 
)2. Hydrate ot barytes 76 

13. Carbonate of barytes 87 

14. Sulphate of barytes J02 

15. Nitrate of barytes 106 

Fig. Wt. 

16. Muriate of barytes 90 

17. Sulphate of alumine 49 

18. Nitrate of alun)ine 5,'? 

19. IMuriate of alumine 37 

20. Alum 272 

21. Potasiurctted silex, 

or glass 37 

22. Superpotasiuretted 

silex 129 

23. Potash, silex, & lime 135 

24. Pola^h, silex, & ba- 

rytes 155 

25. Fluate of silex 60 

26. Subpotasiurelted * 
ammonia 54 

27. Oxymuriate of ole- 
fiant gas 41 

* The olive coloured substance obtained by heating po.- 
tasium in ammoniacal ga?, by Gay Lussac aiwl Thenard, 
Davy, &c. 


PLATE 7. Fig. 1, 2, and 3. represent profile views of the 
disposition and arrangement oF panicles constituting elastic 
fluids, both simple and compuund, but not mixed ; it would 
bediflicult to convey an adequate idea ot the last case, agree- 
ably to the principles maintained, page 1 90. — The principle 
may, houever, be elucidated by the succeeding figures. 

Fig. 4. is the representation of 4- particles of azote with 
their elastic atmospheres, marked by rays emanating from 
the solid central atom ; these ravs being exactly alike in all 
the 4 particles, can meet each other, and maintain aa 

Fig, 5. represents 2 atoms of hydrogen drawn in due pro- 
portion to those of azote, and coming in contact with them ; 
it is obvious that the atoms of hydrogen can apply one to 
the other With facility, but can not apply to those of azote, 
by reason of the rays not meeting each other in like circum- 
stances ; henct, the cause of the intesine motion which 
takes place on the mixture of elastic fluids, till the exterior 
particles come to press on something solid. 

PLATE 8. The first 16 figures represent the atoms of 
different elastic fluids, drawn in the centres of squares of 
dififerent magnitude, so as to be proportionate to the dia- 
meters of the atoms as they have been herein determined. 
Fig. I. is the largest ; and they gradually decrease to fig. 10, 
•which IS the srcallest ; namely, as under. 

Fig. Fig. 

1. Soperfliiate of silex 9. Oxymurialic acid 

2. Muriatic acid 10. Nitrous gas 

3. Carbonic oxide 11. Sulphurous acid 

4. Carbonic acid 12. Nitrous oxide 

5. Sulphuretted hydrogen 13. Ammonia 

6. Pliosphuretted hydrogen 14. defiant gaa 

7. Hydrogen 15. Oxygen 

8. Carburetted hydrogen 16. Azote. 

Fig. 17. exhibits curve lines, by which the boiling point 
of liquid solutions of nitric and muriatic acid, and of am- 
monia, of any strength, may be determined. They arc 
representations of the results contained in the preceding 
tables relative to these articles. It any point be taken in 
one of the curves, and a horizontal line be traced to the 
margin, the strenglii per cent, by weight of the liquid will 
be shewn ; and if a perpendicular line be traced to the top 
the temperature at which the liquid of that strength boila in 
the opeQ air will bu found. 


xJlS it is nearly two years since the printing 
of this second part commenced, it may be ex- 
pected that in the rapid progress of chemical 
investigation, some addition has, in the in- 
terval, been made to the stock of facts and ob- 
servations relating to the more early subjects 
herein discussed. The ground upon which I 
determine the weights of the ultimate particles 
of the metals, has not yet been entered upon. 
This will occupy a leading place in a second 
volume, when the metallic oxides and sul- 
phurets come to be considered. It will be 
observed, that I have seen reason to change 
some of the metallic weights which were 
given in the first part ; and it is probable, that 
in our future investigations these may be again 
changed ; this will depend upon the precision 
with which the proportions of the elements of 
the metallic oxides, sulphurets and salts, shall 
be obtained. The identity of tantalium and 
columbium seems to have been ascertained by 


Dr. Wollaston. Mr. Davy, and the French 
chemists Gay Lussac and Thenard, have fur- 
nished a number of facts and observations on 
various subjects, resulting from their applica- 
tion of the new metals, potasium and sodium, 
and Voltaic electricity, to chemical investiga- 
tions. When the mind is ardently engaged in 
prosecuting experimental enquiries., of a new 
and extraordinary kind, it is not to be ex- 
pected that new theoretic views can be exa- 
mined in all their relations, and formed so as 
to be consistent with all the well known and 
established facts of chemistry ; nor that the 
facts themselves can be ascertained with that 
precision which long experience, an acquaint- 
ance with the instruments, and the defects to 
which they are liable, and a comparison of 
like observations made by different persons, 
are calculated to produce. This may appear 
to be a sufficient apology for the differences ob- 
served in the results of the above celebrated 
chemists, and for the opposition, and some- 
times extravagance, of their views. 

All the phenomena of combustion are exhi 
bited by heating potasium in fluoric acid gas 
(superfluate of silex) ; though this would seem 
to intimate that the gas contains oxygen, yet, 
as Mr. Davy properly observes, heat and lighl 


are merely the results of the intense agency of 
combination. It is remarkable that hydrogen 
is given out, yet not so much as would be 
given by the action of potasium on water ; it is 
variable, and amounts generally to less than 
4th of that quantity. Mr. Davy and tKe 
French chemists agree in the belief of a decom- 
position of the acid ; but it is doubtful whether 
the hydrogen is from the potasium or the acid. 
The fact, I have observed, page 286, of the 
diminution of a mixture of hydr«gen and fluoric 
acid gas by electricity, is one of the strongest 
in favour of the notion that the acid gas con- 
tains oxygen. 

Muriatic acid has been a great object of in- 
vestigation. Mr. Davy's ideas on this subject^ 
in his Electrochemical Researches, 1808, were, 
that the acid gas contains water in a combined 
state ; or, to use my own phraseology, that an 
atom of real muriatic acid combined with one 
of water, formed one of the acid gas ; hence, 
in burning potasium in the gas, the potasium 
decomposed the water, the hydrogen was li- 
berated, and the oxygen joined to the potasium 
to form potash, with which the real or dry 
acid immediately united. This conclusion was 
plausible ; but it was truly astonishing to see 
the French chemists draw the same conclusion 


from their views of the subject. They should 
have viewed muriatic acid gas as the pure acid, 
which combined with the potash of the pota- 
sium, and liberated its hydrogen. Mr. Davy 
has recently written an essav on the oxymu- 
riatic and muriatic acids, with a copy of which 
he has just favoured me ; in this, he discards 
his former opinion of the gaseous combination 
of acid and water, and adopts another, that 
muriatic acid gas is a pure elastic fluid, result- 
ing from the union of hydrogen with oxy mu- 
riatic acid, which last he conceives to be a 
simple substance. This notion agrees so far 
with mine, as to make hydrogen the base of 
muriatic acid ; but I cannot adopt his consti- 
tution of the acid. Mr. Davy now considers 
the hydrogen liberated, by the combustion of 
potasium in muriatic acid gas, as proceeding 
from the decomposed acid, and the new com- 
pound an oxymuriate o^ potasium. The expla- 
nation I prefer is, that the hydrogen proceeds 
from the potasium, and the undecomposed acid 
gas unites to the potash. 

As to oxymuriatic acid. Gay Lussac and 
Thenard have reported some very striking and 
unexpected properties of it which they have 
discovered. They assert, that dry oxymuriatic 
acid gas was not decomposed by sulphurous 


acid gas, nitrous oxide, carbonic oxide, nor even 
nitrous gas, when these were dry ; but ihat it 
was immediately decomposed by them if water 
was present. These inai) appear to them to 
be tacts ; but certainly they are too important:, 
and some of them too ditlicultly ascertained, to 
be believed merely upon the assertion of any 
one. By what means were they found ? What 
was the structure of the apparatus, the quantity 
of gases operated upon, the time they were al- 
lowed to be in contact, the means employed to 
investigate the results, &:c. &;c. ? To answer 
all these enquiries satisfactorily, would require 
a volume in detail ; yet, Gay Lussac and The- 
nard have not said one word. Now, we know 
that the facts respecting the mixtures of these 
gases over water, are not as above stated. Mr. 
Davy observes, (Researches, page 250) that 
** oxygenated muriatic acid and nitrous oxide 
" were mingled in a water ap[ aratus ; there 
" was a slight appearance ot condensation ; 
" but this was most probably owing to absorp- 
" tion by the water ; on agitation, the oxy- 
" genated muriatic acid was absorbed, and the 
" greater part of the nitrous oxide remained un- 
" altered." I have repeatedly mixed carbonic 
oxide and nitrous gas with oxymuriatic acid in 
a water apparatus ; the former mixture ex- 

554- xirrr.NDix. 

hibits no signs of chemical union for several 
seconds ; afterwards, if the sun shine upon it, 
chemical action commences, and continues 
somewhat slower than that of oxygen and ni- 
trous gas ; but if the mixture be put in the 
dark, it \vill remain for days, I believe, with- 
out any change. The latter mixture, or nitrous 
gas and oxymuiir.tic acid, in equal measures, 
over water, produces an instantaneous union, 
muc h more rapid than that of oxygen and ni- 
trous gas, and which to all appearance seems 
independent upon the water. Now, if these 
simple experiments give such dilTerent results 
in different hands, what may we expect of the 
coniplex experiments, where the gases are pre- 
viously dried, and then mixed in vessels quite 
free from mercury and water, and lastly ex- 
amined after such mixture has taken place, 
regard being still had to the effects which mer- 
cury and water have, or are supposed to have, 
upon such mixtures ? 

Mr. Davy has given several experiments to 
shew that oxymuriatic acid combines with hy- 
drogen to produce muriatic acid ; but none of 
them appears to mc decisive. When equal 
measures of hydrogen and oxymuriatic acid 
were introduced into an exhausted vessel, and 
fired by an electric spark, the result was a 



slight vapour, and a condensation of -^V to ^V 
of the volume, the gas remaining being mu- 
riatic acid. This fact, if it can be relied upon, 
is favourable to the notion it is to support ; I 
should have expected a condensation of 4 or 4- 
of the total volume on the common hypothesis ; 
if the author had described the apparatus and 
quantity of gases submitted to the experiment, 
with the mode of determining the quantity 
and quality of the residual gas, it would have 
assisted in any future enquiry on the subject ; 
it is certainly an important experiment. Mr. 
Davy allows the hyperoxymuriate of potash 
to abound with oxygen. He supposes the 
oxygen to be attracted by the potasium, or the 
potash, rather than by the oxymuriatic acid. 
The facts appear to me to draw the other way 
much more powerfully. We find oxymuriatic 
acid in conjunction with much oxygen, in se- 
veral other salts, but potash no where, except 
when joined to this acid. 

Some observations on nitric acid, and the 
other compounds of azote and oxygen, have 
been made by Gay Lussac, in the 2d vol. of 
the Memoires d'Arcueil. He contends that 
one 7neasnre of oxygenous gas unites to two 
vieasitres of nitrous gas to form nitric acid, and 
to three measures to form nitrous acid. Now 


I have shewn, page 328, that 1 measure of 
oxygen may be combined with J. 3 of nitrous 
gas, or with 3.5, or with any intermediate 
quantity whatever, according fo circumstances, 
which he seems to allow ; what, then, is the 
nature of the combinations below 2, and above 
3, of nitrous gas ? No answer is given to this ; 
but the opinion is <^ounded upon an hypothesis 
that all elastic fluids combine in equal measures, 
or in measures that have some simple relation 
one to another, as 1 to 2, 1 to 3, 2 to 3, &c. 
In fact, his notion of measures is analogous to 
mine of atoms ; and if it could be proved that 
all elastic fluids have the same number of atoms 
in the saine volume, or numbers that are as I, 
2, 3, &c. the two hypotheses would be the 
same, except that mine is universal, and his 
applies only to elastic fluids. Gay Lussac 
could not but see (page 188, Part 1. of this 
V7ork) that a similar hypothesis had been enter- 
tained by me, and abandoned as untenable; 
however, as he has revived the notion, I shall 
make a fev,- observations upon it, though I do 
not doubt but he will soon see its inadequacy. 

Nitrous gas is, according to Gay Lussac, 
constituted of equal measures of azote and oxy- 
gen, which, when combined, occupy the same 
volume as when free. He quotes Davy, who 



found 44-.05 azote, and 55.95 oxygen by 
weight, in nitrous gas. He converts these 
into volumes, and finds them after the rate of 
100 azote to 108.9 oxygen. There is, how- 
ever, a mistake in this ; if properly reduced, 
it gives 100 azote to 112 oxygen, taking the 
specific gravities according to Biot and Arago. 
But that DaVy has overrated the oxygen 12 
per cent, he shews by burning potasmm in ni- 
trous gas, when 100 measures afforded just 50 
of azote. The degree of purity of the nitrous 
gas, and the particulars of the experiment, are 
not mentioned. Tiiis one result is to stand 
against the mean of three experiments of Davy, 
(see page 318) and may or may not be more 
correct, as hereafter shall appear. Dr. Henry's 
analysis of ammonia embraces that of nitrous 
gas also J he finds 100 measures of ammonia 
require 120 of nitrous gas for their saturation. 
Now this will apply to Gay Lussac's theory in 
a very direct manner ; for, according to him, 
ammonia is formed of 1 measure ot azote and 
3 of hydrogen, condensed into a volume of 2 ; 
it follows, then, that 100 ammonia require 75 
oxygen to saturate the hydrogen ; hence, 120 
nitrous gas should contain 75 oxygen, or 100 
should contain 62.5, instead of 50. Here 
either the theory of Gay Lussac, or the expe- 


rience of Dr. Henry, must give results wide of 
th truth. In regard to ammonia too, it may 
farther be added, that neither is the rate of 
azote to hydrogen 1 to 3, nor Is the volume of 
ammonia doubled by decomposition, according 
to the experiments of Berthollet, Davy, and 
Henry, made with the most scrupulous atten- 
tion to accuracy, to which may be added my 
own. — There is another point of view in 
which this theory of Gay Lussac is unfortunate, 
in regard to ammonia and nitrous gas j 1 mea- 
sure of azote with 3 of hydrogen, forms 2 of 
ammonia ; and 1 measure of azote with 1 of 
oxygen, forms 2 of nitrous gas : now, accord- 
ing to a well established principle in che- 
mistrv, 1 measure of oxv^en ought to combine 
\vith 3 of hydrogen, or with onehalf as much, 
or twice as much ; but no one of these com- 
binations takes place. If Gay Lussac adopt 
my conclusions, namely, that 100 measures of 
azote require about 250 hydrogen to form am- 
monia (page 433), and that 100 azote require 
about 120 oxygen to form nitrous gas (page 
331), he will perceive that the hydrogen of the 
former would unite to the oxygen of the latter, 
and form water, leaving no excess of either, 
further than the unavoidable errors of expe- 
riments might produce \ and thus the great 


chemical law would be preserved. The truth 
is, I believe, that gases do not unite in equal or 
exact measures in any one instance ; when 
they appear to do so, it is owing to the inac- 
curacy of our experiments. In no case, per- 
haps, is there a nearer approach to mathema- 
tical exactness, than in that of 1 measure of 
oxygen to 2 of hydrogen ; but here, the most 
exact experiments I have ever made, gave 1.97 
hydrogen to 1 oxygen. 

I shall close this subject, by presenting two 
tables of the elements ot elastic fluids ; they 
are collected principally from the results already- 
given. in detail, with a few small alterations or 
corrections ; the utility of them to practical 
chemistry will be readily recognised. 



Tables of the elements of elastic fluids ; 
rature and pressure. 

(TABLE 1.) 

at a mean tempe- 

\Vt. of an 




No. of atorrj 

Niraei of the gases. 


cubic inch. 


ui an atom 

ill a given 

Afmospheric air 


I ,00 


yj 1 



1 .000 














IMurimic acJd 












Oxvmur. acid 





) 060 

Nitrous gas 






IMiirous oxide 






Carbonic oxide 






Carbonic acid 






Sulpliiirous acid 






Olefiant gas 

6 4 





CarburetiL-d hyd. 




1 00 


Sulphureted hyd. 




1 00 


PJiosphur. hyd. 




1 00 

1 000 

Superflu. of silex 






(TABLE 2.) 
Proportions of the constituent principles of compound gase.'^. 

K3we«oFtherom.',Constituent TiTinciplej of loo measures 
pound ga^es, of the compound gases. 

Measures. Measures. 

52 azote +1^3 hyd. 

100 oxycj 
46 azote 
99 azole 

Ammon. gas 


Nitrous gas 
Nitr. oxide 
Nitric acid 
Nitrous acid 
Oxym. acii 

ISO nit. gas 
360 nit. gas 

4- 200 hyd.* 
+ 55oxyg 
-f- 58 oxyg 
+ 100 oxy. 
4- 100 oxy 

150 mur. acid + 50 oxy. 

Sulphs. acidjlOO oxvgen -\- sulphur 
"I00sulph<. acid'-i-50oxy. 

ic. ;>cicl 


Cart), oxide 
Carb. acid 

47 oxy. 
100 oxv. 

Carbur. hyd. 200 hvdr. 
Olefiant gas 200 liydr. 
Sulph. hyd. lOOhydr. 

Wnr. of am. 
Carh. of am. 
Subc. of am. 

100 mur, acid 

+ charcoal 
4- charcoal 
-}-lpart char 
+ 2 parts ch 
-|- sulphur 
4- 100 am. g 

100 carb. acid -f" 80am. t^. 
100 carb. acid -\- 160atn.g 

Constituent principles of irov/cigfct 
of the coinpuund giites. 

83 azote -f 17 hvd. 
87 oxy. 4- 12.5" hyd. 

42 azole -|- 58 oxygen 
59 azote -f- '^^ oxygen 

27 azote +7 3 oxy. 

33 azfile ■\- 67 oxy. 

76 mur. acid -|- 24 oxy. 
52 oxy. + "l-S sulphur 

79; sul. acid -f 20ioxy. 
55 oxy. -|- 45 chare 

72 oxy. -}■ 28 chare. 

27 hyd. +73 chare. 

15 hyd. 4- 85 chare. 

7 hyd. 4- 93 sulph. 

65 mur. acid -}- 35 am. gas 
7(i carb. acid -\- 24 am. gas 
61 carb. acid -f- 39 am. gas 


*" 1 believe 197 is nearer the truth. 


J'U(/r 5 


10 .21 19. 13 U 15 16 17 18 



W SI i'2 23 24- 




98 ?9 30 31 


J.3 34 





J.3 r\ i9 

oo ooo 

(DO CDOCD 00)0 


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- c • 

ili -17 i8 "IS 

•o o#o ®o o®o 

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0®0 ©CD G 


• ^^^^Sb • 

/ivr/. \V(dt Sul/iJi.i^p/ii'Sph 

Sul/jhur inilipUuspk 



.5 a 



®O0 0® ®® 



T ^ yj ^ ^ ^ 
















21 2^ 


2X 25 

Hydro o'eii gas 

Nitrous gas 


(Carbonic acid e;as 



(- -t 

\ \' ^ / 


/ / 


X 1 












Dalton, John 

A new system of chemical 


Physical 8t 

Applied Scl,